I just bought a new cheap one and am going to try to incubate too. It's a little giant but that was what was in the budget. No fan, no turner. I'm home all the time so I can turn them. I won't forget...it is this big white box that will be in my way. I will buy a hydrometer.
I suspect humidity recommendations are a lot like the advice you get when your plants turn yellow...you watered them too much, or you didn't water them enough.
I read about the differences between wet and dry incubation and am going to go dry and depend on the ambient humidity. I think there are more problems with too much rather then too little. I'm going to aim at 35-45 the first 18 days, and higher for lockdown.