e46 M3 can be from mid-teens to mid-30k, depending on what condition/mileage you're looking for. The e90's are only about $5k more for similar examples from what I'm seeing. It's all about what you want from a car. I've driven both and prefer the e46, as the e90 just feels too big/heavy for the engine. I had the chance to drive an e90 M3 and e39 M5 back to back, and the M5 was a better car, IMO.
Regarding how reliable the M3 is, you just need to be prepared to cover the cost of preventive maintenance, and do it up front, rather than wait for it to break. Replace the cooling system at 90-100k miles, rather than having it fail while your driving, and risk a blown head gasket. Replace the suspension at 90k, so that the car doesn't feel like an 80's Cadillac. Replace fluids at regular intervals, and just keep on top of things, and it should run for quite a while. If you do like to wrench yourself, they aren't bad to work on. You just need to add some extra tools to your kit, as the Germans love messing around with fasteners (torx, reverse torx, etc.).