to the original poster,
if you find an e46 you're interested in, and it has over 80k miles, make sure the following items have been addressed.
1) oil separator/crankcase vent valve with all 4 breather lines replaced.
2) eyeball bushings replaced.
3) oil filter stand gasket replaced.
all bmw's have cooling issues, but the parts are less expensive than a Volkswagen/Audi group car.
if you work on your vehicles yourself, then a 99/00 would be a better choice for you, they have electric fans instead of the viscous fan, which means you can remove the fan and get to the front end where most of the common cooling components are, i.e. stat, water pump, radiator, etc.
yes, window regulators are a common failure, but are very easy for even diy'ers to do.
whatever you do AVOID and e46 with an M56 motor, it's a california emission car.
AND make sure the vehicle had it's oil changed every 5-7k instead of 15k....you will know when you pull the valve cover. below is a 15k oil service top end
this is 5k