Some people have made a very high appreciation in R15 and R8, some higher than the privately planned masterplans like Aldea Zama, Selvazama, and Tulum 101, It depends on the investor some prefer buying at a higher price per sqft with all the infrastructure already in place and some will try to get a better deal and wait for the infrastructure to arrive, it all depends on your risk tolerance and your goals, needs and wants. 

I think a lot of folks would be better off if there were more homes litke this being built today. 

The electrical alone will cost you $20k...Don't coat the old sewer line, just do all new...I never had a great experience with the re-coats, better to just run new ABS and be done with it.You're only allowing $125 SF for the ADU....I know it's Texas but I doubt that gets 'er done.PM me if you need more help, I just think you're a little off on your budget.

You will get much better advice from that person than boilerplate legal docs off a website.

If they appreciate at all, that would make me feel better about the deal.

Better value for your investment dollars.3.

Or perhaps, is it better to simply flip a mobile home when using hard money?

You may not know any better (I see it all the time). 

Cost of living is better than Raleigh and Charlotte. 

I don't know much about the market where you are, so if there are agents or investors in your area, they would be able to guide you as to which may be a better option.