Many roads lead to rome :-)
The advantage of a VPS is that it runs outside your home and is 24/7 online. At home in most cases you don't wan't a computer running 24/7. But surely you can buy a PC and run several instances with different brokers. But if i remember correctly i don't know if it's allowed to run Z1 and Z2 at the same time with the same broker!? There was something JCL posted somewhere.... But i can be wrong...