Vacation Rental - 2nd Alternative

Do you have to buy a condo to have a vacation rental? Do most businesses buy their retail space? No. Therefore, could you rent a condo and use it as a vacation rental in San Francisco? Unless the lease says otherwise, this may be a great opportunity. I envision a 10 day per month "free" condo in SF every month. Yes, nothing is free. The other 20 days will be about working the rental. So? Maybe? I think this is worth some consideration. Any ideas?