Model # matters. If it's a 5000, I would take the opportunity to upgrade. If it's an 8000, call Wizard and get the details for each option.
I rented for 1 1/2 years and then purchased. (with a line-of-credit from the bank) There were varied reasons for this. Your business organization (Sole Prop, inc. ... changes things some) as well as your capitalization (how much $$$ do you have available) and other factors can effect the decision. you probably should talk to your accountant.
Personnaly, I would not assume a 5000 rental, but would do a detail analysis of the options for an 8000.
Oh yeah, if that shop has been renting for a time, Wizard may give you soem credit toward purchasing it. Check out what the purchase price of THAT used machine would be from Wizard. You might be pleasantly surprised. A really good deal would alter my comments about the 5000 vs. 8000 debate.