The DU is a group composed mainly of ROM dumpers and arcade game collectors working to preserve old arcade game data. We have access to used arcade game PCB markets in a growing number of countries. We buy old arcade boards with our own money but we also accept PayPal donations. All donations go toward buying old, undumped games and occasionally paperwork needed to fully document game hardware. Keep in mind, though, that buying any used game is "a crapshoot". Games can get damaged in the mail, we can get flat-out lied to, or anything in-between. Our guarantee is simply that "we'll do our best".
If it's an easy dump with no complications, it gets put up for sale. Funds from reselling (recycle funds) go toward more games. Some games never resell or resell only at a small fraction of the price we paid. Some games have to get sent to certain members for extra work beyond dumping ROMs and take months or years before they can be resold. Generally speaking, there is a partial to total loss taken on almost every game.
Maybe, but probably not. Send a PM to Smitdogg. These days we have already dumped everything that is remotely old and common and are basically at the mercy of what happens to pop up for sale. You can't really search for specific old undumped games anymore, at least not with any success.