1980 320i Repair Costs

I'm interested in buying this 1980 320i from a friend of mine for around $400-$500, with only a couple of things wrong with it. Known problems, anyway. I have yet to test drive it and will get around to it this saturday, but as of now my friend tells me that the car needs the following -

New Brakes
New Exhaust
Four new tires
Some rust blasted off from underneath rear windows, can be done by friend

As this is my first BMW I don't know if the prices are varied from other cars, or what. If anybody can give me a guesstimation of how much they think this'll all come to, I'd gladly like to hear it. Thanks.

goto an online parts source to price out what you would need, like bmaparts.com or autohausaz.com

FYI, there are some people who are parting out 320i's, so you can get working parts for a lot cheaper than new.
I actually have some parts from my 81 320i that you might be able to use for this 'new' car:
-pair of front brake calipers w/ pads & hard-brakelines
-pair of rear shoes
-stock muffler
(PM me if you think you might be interested in any of these)
here's a link to a photogallery of all the parts I should have still available: http://community.webshots.com/user/jbob320isale

tires are pretty cheap for the stock 13" wheels (checkout tirerack.com or tires.com for prices). stock dimensions are 185/70/13 (a 205/60/13 is a nice upgrade).