There selling me a 1990 BMW 525i for 1300 bucks. No problems with it. Is it a good deal?

sounds like a fair price. Check for rust above the lisence plate and in the door corners. the manual transmission tends to be more reliable then the automatic. other than that check for any signs of leaks. a rear main seal can easily cost more to fix than the whole car.

Be careful with the m30 engine, the timing belt needs to be replaced regularly.