I am fine for long term growth and don't mind working for the next 20-30 years to build a sustainable portfolio with no mortages on them as the end game plan.What would you do? 

Your plan to buy a property in New Braunfels, TX, and use it as a Short-Term Rental (STR) while you're on the road is solid but challenging with a $200k budget.

Level of Review: Projects are required to submit a substantial amount of project specific information as part of both the application review, approval/legislative process and contract reimbursement process.

A delay in closing is not only inconvenient, it may increase the cost of the loan.Understand the Terms of the Loan: Carefully review your loan documents, including the closing statement, before you close on the loan.

Are they paying below market rent because the landlord hasn't increased rent over the years (eg long term tenants with no increase) or were they rented that way (ie low rent either to fill or because landlord didn't know what market rent was)?

Keep in mind that the changes made to STATE approved contracts will vary.

In terms of ownership, property can be owned by foreigners via a fideicomiso.   

I'm assuming that I could probably do an STR in Lakeland Florida, but don't think because of the location that I'd get good revenue.Who can give me some insight as to whether doing something like this or mid term for nurses has been beneficial for a 5 bedroom 3 bath house.

If possible, I would love to get a seasoned property manager's opinion on my most liked properties in terms of rental potential, etc.

You can be good enough at REI that people will give you their money to invest with them giving you a cut of the profits, or wholesaling where you find a buyer to assume your contract before closing.