Tenant wants a loan for an a/c

[Kush Khandelwal]

The a/c in my unit broke down in my rental unit and it may take a week to get it fixed. 

The tenant wants to buy a portable a/c as currently it's hot in Atlanta.

They are requesting to buy 2 units from a nearby store and then return the units when the a/c is fixed. 

However they don't have cash or credit card available. They are asking if I can buy the units for them and they'll return in time.  What can I do to protect myself, to make sure they return the units in the required condition / timeframe to the store? 

Thanks