That's the best attitude to have.

I've seen WAY too many things bought "as investments" (guns, comics, toys, cars) that just make me want to giggle at the purchasers. Especially those that don't understand how the market works...

Look at one of the buyers guides (toys, comics and guns). Look at the price listed. Deduct 40-50%, if you plan on selling to a dealer or store. That's the best you'll get. Assuming said dealer or store is willing to buy...

Private sale, or auction? Dice roll... you may get lucky, you may not.

I have a few items around here that MAY yield a profit if sold: couple of guns, one blade, and a couple instruments. Not why I bought them, but they MIGHT give a profit...

The more niche the market, the worse your odds.