Things to look,a lot actually,first and the must one,get it on to the ramp and get it inspected by someone who knows these cars,pay special attention to sub frame mounting points-they crack alot.Next is full diagnostics,vanos test is a must,when you can move on to the diff,look for half-shaft tightness,gearbox gives problems too,2nd 3rd gear syncros,and then bodywork.If you manage to get a good one you will enjoy it big time,but if you unlucky and get your self JUST A "clean one " it will get you in a big hole,because parts for second hand parts still very expensive and very hard to come by.