Thanks for the insight/info.
Just start picking up old boxes from your neighbors or from garage sales... If they have a Vista, Win7, or Win10 key on them, they're worth parting out at the least... And in my experience, most can be resurrected easily - Normally just a virus infection, or a toasted hard drive...
It'll give you practice and a little depth... And maybe some money, while you learn.
When you get ready to build one, start a thread for it in tech... I'm sure folks will be happy to help you out...