My 01 E46 3 series started to cost me money at 100k + and was the first round of fixing things in its life.....so whatever Beemer your looking at try and see if the previous owner has put money into it it will mean you will not have to.
Suspension and lower control arms are getting tired at that mileage and will need replaced,the cooling system will need a complete overhaul,check the window switches all work,rubber intake boots crack and leaks are hard to spot but throw srs codes its probably a good idea to replace the fuel pump and filter for insurance too.
Motors are solid and last forever,if you can turn a wrench I would say go for it if not budget a few thousand dollars a year for maintenance,