Hi,
I don't know about the rest of you but I'd not buy any camera for investment when it's too new. The time to buy is when they are an "old" and "obsolete" camera, meaning opening on ebay for 99p and then selling for a few hundred, perhaps. Then wait for a good one in working order or else a good looking one and have it repaired. Use it a bit and wait for the right time to sell it.
The only alternative is rummaging through the flea markets and being lucky. But even then you have to be prepared to waste a film on it and then there's the worry of selling it at the right time.
Buy new or a year or two old to use and get your money's worth, is how I see it.
Regards, David