I pretty much agree with what others have said.
1. Definitely get a PPI from a reputable shop. Talk to the guy doing the inspection. This will basically be a mechanical inspection, but get a list of all the things that will be done during the inspection so you can go over it with the tech.
2. Review the service records from the BMW dealer that serviced the car. If the SA there won't give it to you, ask the prior owner to get the records for you.
3. Ask the owner (if he is impartial, which he may or may not be) how much oil the car uses between changes and how often the oil was changed. There is no "right" answer here as BMW spec allows for quite a bit of oil use. The best case scenario is oil changes at least every 7500 miles (e.g., double what the computer says is "needed"). For a MY 2002, acceptable oil use between 7500 mile oil changes (IMO) is essentially none if TWS 10-60 is used and approx. 1 to 1.5 qt for 5-30. Obviously oil use partially depends on driving style, so factor this in.
4. Be prepared NOT to buy the car if you fly out there and all is not as it should be. This is the hardest thing to do, as every inch your being will want to drive off in the M5. Visually inspect the car, look for evidence of prior painting or body work. Then, of course, DRIVE the car. It helps if you have driven a good example before, but make sure you do some hard 1-2 and 2-3 shifts and check for clutch slippage. Despite what the dealer may think, you have not bought the car yet!
5. Side mirrors don't fold up = broken, as this was a standard feature as I recall.
6. LFCO9, the lights pictures are the 2001-2003 freshened angel eyes sold in the US. While some people change the bulb to a silver one for a cleaner look, any true clear corner angel eyes in the US are after-market.
Good luck!