The land has to be zoned RV to collect lot rent

We drove by the house today and one of the cars on the driveway on the side of the house has graffiti written in red with the word "whore".

well that iss the other red flag, the seller on their listing is writing what the rents are and then calling it the "potential gross income".  

You can use Zillow to find comps, but I would just present it as "123 red road sold on xx/xxxx for $100,000. 

Use good quality waterproofing (think Red Guard versus a sheet of plastic) when doing tile jobs.  

A lot of new home construction is going on in Ooltewah (zip 37363) and it's outside Chattanooga's property tax zone, but prices tend to be very high.

Not a big red flag really.

Is this typically a red flag regarding the condition of the property?  

I went on Thursday of last week but I had no idea what I was looking at and I was too shy to ask the women that worked there (I know, got to get out of the comfort zone - but look, give me a break, I'm naturally shy and I at least walked in and got to the files; that's progress).

Check with the local town zoning.