If you do have a pet free unit though it is my understanding that you have the right to have it returned in the same condition so it seems fair that they are responsible for carpet cleaning and I would go for air duct as well. 

Some of my places don't have central air, just window units. 

I would also look at a duplex , triplex or 4 plex so you can Air BnB if allowed or have the other tenants help pay the mortgage while building equity.

Have you been changing the a/c air filters?

@James Feely I use Google Forms to pre-screen potential applicants before sending them the link to my Cozy listing & application.

Buy a couple beach front properties (Panama City) and Air bnb?

We live in the suburbs of Portland Oregon and air conditioning is more of a bonus not expected here, especially in older homes.

Once we cleaned and vacated the property - we kept it open as much as we could so the property would air out.  

I use Zillow, FB, and Cozy @Curt Bixel. 

The eviction moratorium, high unemployment, federal stimulus up in the air...