I'd like to see compression #'s and pull the codes if your going to spend that much $. These two items at least will let you know some info on engine condition and any problems it may have.
Bring a friend thats not interested in the car,so they can give you honest feedback about the car. Bring coveralls so u can climb under the car. Ask for reciepts for parts, labor and maintenance. Ask if you can have the car inspected by a mechanic at your expense.
And the best advice i can give is to not need the car. You should always be willing to walk away, you can always find another car. I have saved thousands on buying cars because I walked away and came back a week or 2 or 3 later. My most recent purchase blue booked at 3600, was for sale for 2200 originally, and I just bought it for 800. Not a 5.0, but the rules are the same. the only thing this car needs is tires.