Al, IMHO: The best value to be obtained by ownership of a model is pleasure which is derived by it's very ownership and use, not the resale value. If you are a collector, and you have fun collecting and displaying them, then go for it! If you are a modeler, then use it in whatever way makes you happy. In most cases, we are not collectors, and the value is lost if it sits unused with a tear in it's eye. Us non-collector types may render the model useless for resale, but had a heck of a lot of fun along the way. I think the stock market is better suited for investments
That being said, I would think it's greatest resale value would be reached if it were returned as close as possible to factory fresh condition. That is if it's "collectable" and is now or ever will be a "desirable" model. If not, it may be worth more if it is in the most realistic looking and best performing condition (i.e. uprated modern parts). In either case, the restored value may or may not reach the initial investment plus parts, and almost certainly not plus labor.
Usually, the "deal" is made on the buy, not on the sale. It's a lot easier to find something that's for sale for less than it's worth, quite difficult to find a buyer willing to pay even what it's worth. If I were to get into collecting these things, I would get a book or three that tells me what to look for initially, and look for these items in good condition, but under priced.
Perhaps there is a collector umong us that can offer less general sound advice. Myself, I just try to enjoy the journey. You can tell by my avitar that I don't buy the most expensive locos!
Welcome to the-gauge, Al!!!
