Test the dvd and other electronics. Roll down all windows, then back up again noticing speed- this is an indicator of a dragging window regulator. Drive trans in regular then tow mode to listen for trans pump getting way louder in tow mode. worn rear tires and new fronts are usually old front tires moved back, so look t them for a wear pattern that could tattle tale front end component wear if you feel anything a little off in the front end but are unsure. Bring a code reader. Check for codes before you run- if not ready for all test then he cleared some codes before you got there.
I always include a smog test at the end of my test drive. Here a smog test is required and vehicle must be registered and new plates to every new owner anyways. So I let them know in the beginning- at the end of test drive will be a smog test and if it passes I'll buy it, and I pay for the smog. If it fails I will walk home and you can pay for your failed smog test so be honest now if any codes have been hidden or anything in the system is off or its a waste of both our time and their $. I had people fess up before I even looked under the hood...
Oh yeah and the only removing a couple $ for rust? Not here. blue book minus cost of bringing vehicle to that exact condition. $7,000 blue book and needs $2,500 for new parts/labor and paint is a $5,000 price at best.