So selling an annual rental and purchasing vacation rental or air bnb or factory would all be fine. 

We are thinking of listing it with Air BnB but we live an hour and a half north of there.

you already live in a state were investors buy.. not sure why U would wonder about.SC in Charleston particular is very robust.. however do check prop tax's  the play there is LEGAL air bnband student housing..

There are probably State laws that apply as well as local ordinances in some cities.Although I'm not 100% sure, I THINK a landlord is required to keep the rental "habitable" which I think includes things like hot water and a heating system but not things like lawn care or air conditioning. 

I'd need to buy an HVAC unit and air it out for a month after completing repairs.The question is, supposing the land is worth $25,000 and it'd take $30,000 to complete the necessary repairs... is it worth trying to salvage or should I demolish and do something else? 

Hi There,I have a tenant who has been having issues with his air conditioning on and off since last summer.

It's just a fancy exhaust fan that pumps basement air out and up through a PVC pipe going up the side of the home.

Rentometer is excellent but only seems to work for estimating long term rentals vs estimating short term rental income through Air Bnb / VRBOI use Beyond Pricing for Air Bnb but that is a service that helps me maximize price once I have purchased the property. 

Added central air/heat, granite, carpet, vinyl floors, and stove.What was the outcome?

If it is a large raise and the tenants are good you can do it stepwise but if they are going to leave they will still leave so you are prolonging the inevitable.