It sounds like a couple of folks have answered most of your questions. 

Quote from @Gio Kattan: I would check with a local realtor that are doing deals in this area and local PMs in the area that deal with STRs to give you the answer on that! 

I would honestly call three HVAC people to come take a look at it and give you some answers along with pricing.

I can't get a straight answer from the county.Does each unit have its own building permit that would be pulled?

The answer of course depends on your risk profile but did investors even know what the debt was? 

(My contractor often just answers these calls and makes the necessary repairs without me ever knowing).

Overall though to answer your question, there is some supply glut in the RRG area so those older properties with less amenities are struggling some.

To answer the title of your post, selling fsbo can be a good idea if:- you have experience selling RE- you price the home to sell- you have systems in place to collect inquiries and facilitate showings i.e. call center/email/google forms for screening inquiries, showing agent, lockbox, security alarm, etc. - you have dozens of local agents who can market the property for you and bring you a buyer- you are listing in a desirable area with low-inventory - you are not in a rush to sell

You haven't given many details so it's difficult to give you a quality answer for your situation.

If you have a regarded tax entity, e.g. partnership, S Corp, C Corp, you need complete financials -- P&L and balance sheet to adequately prepare the tax returns and answer tax related questions.