I dunno whether you can save that much these days, you can get a solid smart trainer like the Kickr for 500 €/$ these days.
I have had a dumb direct drive fluid trainer for many years, an Elite Volcano, and was very happy with it. Nowadays I use an Elite Suito, but I use it in resistance mode when I do anything above Z2. I would recommend an external power meter, but you can get that afterwards if the budget doesn’t allow for it.
Why do so many people dump on ERG mode?
If your idea is ‘training’, ERG mode seems like the thing to be doing. 
Because erg mode artificially locks you into a set wattage. Ideally one should be adjusting power based on RPE and erg mode stops you from doing this.
You also see people settling in to a single cadence because erg allows this and that has issues once you go ride outside.
Additionally erg locks you in for intervals above ftp (30/15s, vo2 max, anaerobic etc) those should almost always be done all out but with erg you don’t have that option.
Why do so many people use TikTok?
Why do older people think younger people are worse than when they were young?
And other ineffables… 
Assuming the smart trainer power meter reads approximately the same as an outdoor bike power meter, ERG mode takes away the self discipline required to maintain a particular power/pace that you must have when riding outside. So long as the power meters read about the same, that’s the main critique. The unique feature with a smart trainer is the ability to simulate elevation on a virtual course. I’m not much of an indoor rider, so I’ve never done much of either, but ERG is just the equivalent of treadmill running on a bike. Nothing wrong with it, but I am never surprised to read posts from regular ERG rides wondering why they can’t hold that power they usually do when they get outside
I don’t mind erg mode, just watch something and just pedal away.
I try and do the power cadence drills on the rollers
And I quote: “If your idea is ‘training’, ERG mode seems like the thing to be doing.”
Valid points, but so what? Weight training, the weight doesn’t change in between lifts. I mean you could, but what a hassle.
I got lectured by a Garmin support agent on hiw stupid and silly it was to use ERG mode, and was once lectured that the Kickr Bike ‘didn’t do ERG mode’ because it was a waste of time.
The Garmin rep I talked to next was ‘going to take it up with that agent’ and I hope he did. And I laughed at the Wahoo rep that told me their product doesn’t do ERG more.
But there is a nugget of truth, perhaps, in the war on ERG mode as when I first started out on a smart trainer I did develop a faster cadence outside, but hearing that Chris Froome was using a higher cadence while riding gave me a smile.
I guess I don’t ‘free-ride’ much because of my 'killer instinct, the urge to kill/pass people is strong in this one. I would pull until I couldn’t pull anymore because of those urges, and they are my fault.
But ERG mode is very useful to me. But maybe it’s part of being ‘overwhelmed by training tech’. I know I was blown away the first time I rode my used H2 trainer. The first time it adjusted the demand, I almost panicked, and then had a huge smile. If only the Peloton had that feature…
If you are training you should be listening to your body enough to slightly adjust day by day.
Some days riding your threshold intervals at 400w is perfect, other days you might do them at 380w or 410w. If you use erg mode you get to do all of them at 400w.
More importantly with anything over ftp using erg mode actively hampers your training. As I already said these intervals should almost always be done maximally. Since erg mode locks you in to a set wattage it will basically never be correct.
ERG mode teaches you to resist power not to make it, but it’s nice to Z2 and chill sometimes…
I do! I ask myself what I want to do, and then pick a workout, and if needed, hit the bias adjustment, or bail and do a different one.
Again: Bias, and some days I don’t want to push, but my evil neurons say ‘PUSH IT WE NEED PAIN!!!’ and I do push it. I also got into doing ‘active recovery’ and those workouts were killer, but they DID help. I could FEEL that they were helping. I need to do them again too.
Sure, some trainers have lags in short intervals, and that’s just life. I have a bunch of workouts in Zwift that are are popping over FTP repeatedly, and some do active recovery after. I feel people that do workouts that hit over FTP and then dump the resistance to z2 or lower are the ones doing something wrong, especially if they keep doing it over and over again. Prolonging the effort helps train for more higher efforts, but everything in moderation (no matter what Green Day says).
I get it, free riding is emulating ‘real life’, but it’s not. No wind, no hills, no unexpected nonsense, likely lower (or higher) temperatures…
Where is that coming from? That sounds like the ‘If it’s indoors it doesn’t count’ luddites.
I can bust my butt just as hard, and often harder using ERG mode. Free ride and I get tired, I can back off. ERG mode and I get tired, I risk the spiral of death as the trainer eats my will to live. I feel I’ve benefited from being pulled along by ERG mode more than free riding. After some workouts that I literally survived, I feel so much better, almost happy to be abused. But I get free riding. I’ve been doing the Your of Zwift and ripping some PRs on each one so far. Got 5 out of 6 yesterday.
Listen, riding ERG or ‘simulation’ is STILL riding, and everyone gets benefits from it. Riding the couch is what people get nothing from.
RIDE ON!!
This is a lot more hassle that I want to deal with when the alternative is to just hop on the bike, ride until I feel warmed up, execute 3x30 with slight variations in power and cadence based on RPE then cool down and hop off.
I am not talking about erg lag. It’s about the fact that you cannot know your ability on all out intervals without just doing them so locking yourself into a set power on erg mode is counter productive.
If I am doing 1m max efforts I just go max and hang on, I don’t want to have to try and adjust the power up or down mid interval. Even more so when doing sprints.
Similarly with vo2 max intervals I am cross eyed by the last minutes of a 5m interval and trying to adjust power is one thing I don’t want to have to devote any mental energy to.
Honestly, I don’t think is much difference between 3x30 holding wattage or using ERG. From an adaptation point of view, we are talking single digit percentages, maybe. ERG or not ERG is not a game changer. Yes, I know that many coaches and pundits will say that ERG is the devil.
I do think riding the trainer a lot can make you a one trick pony. It locks you in to certain cadences and a not so wide range of torques unlike one would experience outside with varied terrain. Still, not a big deal. One adapts quickly after starting to ride outside after winter.
Personally, I don’t think this is what I would consider bad/is what I dislike about erg mode. It is that it feels very unnatural compared to riding outdoors and the cues to your trainer are reversed. E. g. you need to push harder and “overcome” the resistance if you want to increase your cadence without shifting.
On the trainer, I can stick to power targets within +/- 1–2 W (after the trainer and I have warmed up). Typically, I aim a tad higher, so I am a little over.
In my experience, adjusting the power according to RPE is a thing that almost never happens and almost never works (assuming that your FTP is set correctly). Either I am fatigued or mentally not up to the workout and I select an endurance workout instead. Or my perceived effort is just higher that day, big whoop.
My decision to bail is based on (the ability to produce) power, (the speed of) heart rate recovery and RPE. If just one factor is unusual, I’d typically push through without altering the workout. If two or more factors are abnormal, I’ll consider doing an endurance workout instead.
I don’t think it makes a difference training-wise, so I don’t think it is the devil. Personally, I don’t like it for anything except endurance workouts and I think I can do a better job at sticking to power targets than my trainer (an Elite Suito) in erg mode. If you get used to it/like it, then why not.
I use ERG mode for everything 
It’s worked perfectly well for me and my setup (kickr v5 + Favero PM)
I’m not going to get in to the argument for and against so everyone reading this can feel free to turn it on/off as you wish 
I think these long VO2max intervals are where ERG mode differs the most from standard/resistance mode workouts - but I can see arguments each way regarding which one is “best”. ERG mode are not going to be perfect maximal efforts - but there is absolutely no hiding when to do these on ERG - keep that cadence up or die 
IMC its probably because my Suito doesn’t handle ERG well. I tried it again over Christmas and yet again I’ve got a niggly knee, it happens every time I use it I should have known better 
I see two options…
One) Pedal power and dumb trainer.
A simple approach would be a favero power pedal. This works inside/outside and then use a dumb trainer to get started. The Faveros offer both Bluetooth and ANT+ so in theory work with your existing hardware.
Add a HRM at some point. Other sensors not needed.
Two) Smart trainer and HRM only for outside.
TrainerRoad is rather good at using HRM only rides alongside power rides to guide training. For outside rides, use a HRM and just ride your bike with a general mission, don’t fret about structure.
Ride the turbo for structure and progressions.
! Last time I checked, strava dropped HRM support for the phone app. This was a few years ago. You may need to seek out a used headunit to capture HRM outside.
However, based on your living situation, a direct drive turbo and some additional sound dampening is where I’d focus. I’m also a top flat dweller and would’t dare have used my old wheel-on trainer inside.
YES!!!
I follow a lot of people that ride the Peloton, and not at all to dump on them at all, but many do the Wilper’s ‘Power Zone rides’ and their top intervals are often sagging a bit. Some quit in the middle to catch their breath (been there) and kick it back up for the end. In ERG mode, I know that if I stop on a big interval, I have an even bigger wall to climb to get back to spinning the pedals. Spiral of death is no lie. Oh, and the first time I swapped from ERG to ‘sim’ mode, I hit that wall HARD and felt like I pulled a muscle just trying to get those cranks to turn. I’m not sure what went wrong (probably bad gear? Firmware problem? Simulated flywheel?) but the idea of going to sim mode in the middle of an ERG workout filled me with instant dread but it actually does work well. I’ve done several times now (on a different brand of trainer).
Locally I found so many people that I rode with that were gleefully ripping my history and present of coming from a Peloton to an H2 noisemaker and yet that next winter many of those tormentors had Pelotons and/or where ‘chained’ to their smart trainers.
I feel I am not hiding when I ride indoors, and definitely not hiding from a trainer that takes its orders from the programmed routines in the app I use. I feel more pain more significantly and at higher levels when the trainer drives the route (on challenging routines). Crap on the idea of ERG all you want, but pick a true killer ERG workout with brutal intervals and active recovery and tell me you can get that same effect riding outdoors. YOU CAN’T! Unless you ride in some area perfectly created in a laboratory to impart pain and improvement.
So let’s end the ERG mode sucks BS once and for all…
(BTW, all the IRL coaches and trainers (and authors) people hire that rip on ERG are probably just looking out for their career rather than imparting some nugget of wisdom. They know that if you do your workouts in ERG mode, their usefulness is very limited, or, shock, nonexistent. (They are out of a job))
I have been using foam tiles below my trainer. I upgraded a few weeks ago and added vibration damping tiles (made for washing machines and dryers). No problem, no complaints from neighbors.
I think there is value in doing “best effort” intervals, especially if it is your last one. But you are right, you cannot hide with erg mode. Even struggling is immediately punished.
During the pandemic I was joking with people, mostly on line, that I was a lab rat hoping to get a food pellet at the end of a ride, and yeah, I kinda felt like it at times, but wouldn’t change that for anything. After a couple surgeries, I hope I can get back to that level too. (Stretch more, duh)
(Interesting thought on stretching: I had a Bowflex Power Rod machine and apparently used it as a poor mans pilates table, and after ‘free stuffing’ it, find that I miss it. Who knew that thing was actually so damn useful and instrumental in my training. Now I have a Torque F9, and it’s not the same. Might have to buy a pilates table now, but where to put it. Could it be used as a futon, or a bed? I need creative ways to make the wife think I’m not crazy and spending foolishly 
)