This depends on the cost of the item, the risk associated with not having it, the cost associated with renting it, how wealthy you are, and so on and so forth.

This depends on the cost of the item, the risk associated with not having it, the cost associated with renting it, how wealthy you are, and so on and so forth. No single number makes any sense. A plunger can probably expect <0.1% use of it's capacity. But being stuck without one really sucks, the cost to rent is... once you account for the spent traveling back and forth would be higher than the cost of buying, and as a result literally everyone just buys them. On the flip side a 20 year old fast food worker with $0 in their bank account probably just plain can't afford to have 5x the housing capacity they actually use. That would bankrupt them. So they just don't do it.