I will note that it pays to record everything you do in a journal and with a table or spreadsheet giving dates and prices.
About 5 decades back, my old 57 1/2 ton was primered for years. Meanwhile, I worked the engine, front end and so on over. I was looking at new rigs and asked what that they'd give me. Even though 57 weren't worth much compared to today, the offer was laughable. Then I pulled out the receipts and the journal. The trade in price went way above what it started at.
THEN there is the sad comedy: My 69 1/2 ton had a custom interior that required me to build my own harness (I did a bit of that for a living, working for the feds). The loose-leaf manual I made detailed the wiring diagrams, bulbs and everything needed to keep that one pickup going (tire size, engine specifics, transmissions that would fit, etc.). It even listed the U-joint brand and number that tied the Lemans 4 speed to the drive line. The guy was an expert and didn't need it when he bought the truck. What a dumb ass.
SIDE NOTE: My notes were not average. They were carefully drawn out and clearly printed details. The feds used notes I made on the job to update equipment manuals. So it wasn't like the manual was composed of scribbles.