wiring components and testing in PSU it's hot but additionally it's not necessary but normally the PSU have to connect with the main Line powered mother board and plug the components.
No it depends on your country and type of business if you are running an online gambling site that deal with bitcoin only then i think you don't need any license or registration,
try mining newly launched altcoins, with established coins you won't get much ROI but if you mine a new coin and hold them then you can get some good return