I've got an older mobile home that needs air a couple of weeks out of the year. I don't provide an AC, but I have the framework in place and attached to the outside of the house that is just the right height to set a window AC on.
If the tenant wants AC, they spent a $100 to buy their own and just have to slide it onto the existing stand.
That saves me from damage to the vinyl window frame and the stand is slanted so that condensation drips away from the house. It's also secured so that ordinary tenant abuse can't bring it crashing down on top of anyone.