Unless you have a lot of money to burn, and space for the machine and storage for the cartridges, I would suggest you look into riso print services instead. They are too big, too expensive, and too labor intensive to just buy one and mess around with because you think the style is cute.

Owning a riso duplicator really only makes sense if you have commercial ambitions such as starting a print shop of your own or getting into the independent/self-publishing racket. If you do have commercial ambitions, make sure you are committed to it. I've seen a number of riso printshops suffer from burnout. It seems like for every shop that suspends printing services, 3 or 4 more pop up though. So, depending on your needs, you might be better off seeking out a printshop to outsource your print jobs to.