Value of car purchase? Please, it's complicated!

64dart170
This is a tough one all my kids are still too young to drive, and I think this is a toss up. I know I havent been in this situation. Me and the ol man back in the day put a ton of money in one of my rides and we were on a budget too. When i moved out I needed a dependable driver not a hopped up hot rod. So I told him I was wanting to sell it and asked him what he thought. LOL he said you wil never get what you think its worth son and then proceeded to tell me I was up$*(^ creek and I should have took the offer about 6 months before from a complete stranger whodidnt have a lick of sense. So I sold the truck and went in the hole about 6k counting all the junk me and dad had in it. Now I'm kickin my own but wishing I still had the truck boy was that thing clean. So what I'm thinking is buy it from him and 5 years later when he wants it back make him buy it at the price you bought it plus whatever money you put in it. I know I would buy the old truck back if i could.... My opinion.
Chuck :D