I would check for frame damage. If it was a front end wreck like mine they don't take much abuse to kink the frame rail at the mount for the front subframe. this will be just in front of the motor mounts. Also check the mount brackets, mine broke in my accident and most bmw ones are designed to break away so the engine drops down and below the occupants rahter than through the firewall. Shocks and springs should probably be done soon at around 150k, although i never did my shocks and they were ok... just going through everything that you may end up paying for soon after the sale is the best way to go to see if the car is actually in your price range. I'm very wary about buying a wrecked car because you can never be sure that everything was repaired properly. clutch will definitely need to be done as mine was slipping in and out of gear when i hit 170k. depending on how they drove the car, but judging from the chip i am guessing hard so good preventitive maint. while your in there do the lightweight flywheel upgrade. best mod i made on my car period! What brand chip is it. if its ebay just walk away from the car my friend. if they aren't willing to pay for a reputable chip when making performance mods on their bmw, imagine what they shorted on with general maintenance.
it might help if you posted some pics as well as asking price. if the price is right they are great cars and i loved mine to death, literally (death of the car) motors are like paul said, bulletproof and will take 11psi turboed on the stock internals with no issues. They used this engine for the 5 and 7 series from i think the early 70s through 95 so abundance of parts and knowledge on them are there. The 535i in general was a great car to work on, very simple as long as you didn't dive too far into the electrical systems they have as they get fairly confusing very quickly.
if you have any other questions let me know, i'm always glad to help a fellow enthusiast out!