My land is also buildable and I have plans from an architect for a 3 bd/2 ba home which would cost 300k to build (it's in CA) and is in an excellent STR location...but I'd need a construction loan to build it.

They charge 1% in the form of a closing cost to the buyer.

I added $20k to that to be safe and estimated $100k.I started at $330k and took off the $100k rehab and $10k carrying costs (interest only LOC and taxes, insurance, etc.)

Can you recommend someone for cost segregation and a CPA in the Dallas area?

I got a 3% mortgage, and closing costs covered.

My rough estimate is $3k negative.It happens San Diego YOY price increase of 9% should be enough to barely cover selling costs.  

The answer to every tax question is "it depends" ha!

It is all about if it will helps the sale, in price or time it will sit on the market  which it ultimately comes down to money because of holding costs. 

Depending on location they can cost a lot to replace but when you factor in what you save from paying sewer bills it’s cheaper in long run.It would not stop me from buying a house

Sort of a hidden cost, but still a cost to you.