I'm a realtor in Houston, TX but looking to expand my portfolio to include some rentals and possibly some flips.

If you're serious about this, you should definitely consult an attorney.I am not one, but here are some things I've learned from playing around with these types of things:--Trusts are excellent vehicles for anonymity--You can hire a professional fiduciary (like an attorney) to act as trustee so the public contact is not easily affiliated with you. 

All easily convertible back into a garage if I wanted but by spending less than 20k on each conversion I was able to receive almost all of that back within the first year and then profit year and after.

The problem is if the buyer starts asking a bunch of questions of the agent and follows up and starts treating that agent as if they are their agent, then it might cross over into implied agency at that point if the agent starts doing work for them that a buyer's agent usually does (which showing properties does fall into that category so you can see how it can easily create a situation where the agency relationship is murky without a signed agreement).

Some use Google spreadsheets that way you can keep track of your expenses and income easily.

Work with a real estate agent, analyze potential deals, network with local investors, and expand your portfolio.

I could easily see them raising the taxes to 8-12% within a few years.

You can easily do this on a spreadsheet, and it will take less time to track than finding and learning new software.

The second question is what criteria do you use for deciding when it is the right time to expand your model to look at other opportunities that you may not have considered previously? 

Also can you expand on what NNN is?