The rent price is something I have been looking into and the general feedback seems to be its far too high to begin with so will probably be changing that.
The rollups are meant to be expanded and have a bit more to them in regards to selling, mood boosts and addiction. I just didn't get round to updating them this build.
Scavving doesn't level up. But I think your fitness and intelligence plays a part. Tbh I can't remember.
Glad to hear you are enjoying the game :)