@jblock22 On the bright side, you do have what sounds like a Pi3, which is a supported computer, you have a cabinet someone built with arcade controls, USB ports, a display, and a nice enough design that you were interested in buying it. A build project with just this hardware alone is a serious undertaking, and getting one that looks nice enough to sell is no small feat. Depending on how it was built, you might also have a controls interface of some kind.
Now, the software is the real questionable part of all of this, but you can easily re image the SD card with a known working image from this website and join the community. You will need to open up your system and do some investigating into what exactly you have which might entail some google searching as well, but once you know what you have and you are willing to work with it, you can probably turn this in to a great system. It will take work and interest, but it can be a fun hobby.
Maybe that is not why you bought it, but there could be a silver lining.