Had an '88 535i for several years. The E28 is a great car, but unless the prospect has been maintained, it's gonna nickel and dime you like crazy. They are obviously getting old and everything plastic is pretty crispy now.
Look for rust by the license plate lights, and try the brakes from highway speeds. If there is a shimmy while braking like this, you are looking at all new control arms, probably shocks also. An auto will be no fun. Only go for a manual IMHO.
www.mye28.com
Rgds,
Chris W.
'95 E300D, 404K