My overall answer depends on how you answer the questions above, haha. 

I believe in San Antonio as a whole for long term appreciation but Vida specifically depends on specifics of the home.

I've brokered transactions in Nassau & Suffolk but depending on the area it might not even make sense for you to sell in this current market. 

Raising rents really depends on the laws in your state.

Still, the best card for you will depend on the creditworthiness of the personal guarantor (which I assume is you) including your credit score, recent credit inquiries on your credit, debt-to-income ratio, and the age of your business, and a host of other benefactors.

With a shell, depending on a few things the materials alone can cost 100k before even  bathrooms or windows in.

Each investment strategy has its pros and cons, and the choice depends on individual goals, risk tolerance, and market conditions.

You might get lucky or unlucky if a buyer buys but ends up not choosing you to build.

I have my license with Keller Williams now, but they gave me the option to choose another broker while still paying my full tuition through their prep program so I would also highly recommend Keller Williams as a broker.

In regards to learning more about real estate and maybe how to answer those questions I'd recommend listening to BiggerPockets (Rookie and Real Estate Podcast), there are also some market specific real estate podcast you can check out depending on the area you want to invest in.