I can only say that I would have an independent advisor review the logbooks, service bulletin compliance and forecast maintenance items. Anyone who is selling an aircraft has but one thing in their minds, most amount of money possible and for the most part planes are sold so the owner does not spend a large bundle on a scheduled maintenance action. If a serious issue is found during an inspection I believe it would require correction before the aircraft is released but I would watch for that. Any price can be negotiated but you need to know what the liability is to you if you purchase. Extensive downtime can be expected also with certain programmed maintenance activities. Good example of cost, our 11 year old G550 now needs brakes at 1900 landings. Cost 80K each (times 4).