I keep receipts for the same reason.Never put more into one than you can get out of it.Dont make much sense to build a $20,000.truck that is only worth $15,000.In todays market you have to keep one for a few years before selling to realize a profit.I keep receipts on everything except my labor,I consider that a labor of love or just plain good therapy.If I figured my labor in,even at a minimal rate the figure would scare me to death.