I would rent one to do your son's carpets first maybe? You don't know what kind of dirt and stuff you might find in a stranger's carpets. You might find pet hair, dust mites, flea eggs, other insects that I won't mention because now my skin is crawling. You can buy one for yourself later or are you worried that a rented machine might contain all of the above too? That question presents quite a dilemma doesn't it?