If you are really set on getting into this car I recommend you do the following;
1) Insist to have the car inspected at a BMW Dealership (Here in Canada we have what is called "Certified" it basically means a BMW Dealership gives the car a complete inspection and certifies the work ~ you may have a similar, if not the same program in the US)
2) Get all of the service reports on the car. They should be available at any BMW Dealership.
3) Grab one of your knowledgeable friends that knows cars and go over the results of 1 & 2 above with a fine tooth comb.
If it is a private sale ,,, insist of 1 and 2 above to be done.
Once you do this and you still want the car renegotiate the sale price based on what if any work is to be done as found and identified during the BMW inspection.
Ask this question half way into the inspection, this will do two things a) they will make a good inspection and b) the end result will be as near to the truth as you may come ---> As this is done ask BMW what would it cost me to purchase an extended warrenty for this car, if they are willing to do it then that is a good indication the car has a clean bill of health ... so don't get the extended warranty (save the money for future repairs if they surface, they will be far less then the 7K) ... If BMW is not prepared to sell you extended warranty on the car walk away and find a better car.