Your best off buying an 08 and up. You can read about all the updates but chances are lots have been missed. I bought an 07 last year and I've done a ton of work to bring it up to the updated Phazers and mine had apparently had all the updates done. At 15000 miles expect things like front end components, slopping steering from worn out linkages, idler wheels, drive shaft bearings. Mine only had 6,000 miles and had to do them all.
Good luck and ask for the receipts on the work he's done. If he's owned it since new and has done little to it run for the hills.