Also you should have a GC that walks your properties and gives accurate estimates before you do the inspection.

At this stage, I hope to have enough experience, and the network to be able to accurately estimate total expenses, allowing me to move towards bigger projects with bigger potential gains.Any advice on ways I can move forward with my goals?

That is, the only accurate number here is your purchase price.  

Now, Austin is now becoming California, but if you live here and are renting then you have better options as an owner occupant, than as a pure investor in Austin.If my Assumptions are fairly accurate, then listen up, if not disregard.Buying a new built house in Austin on limited funds, hoping to sell it in two years so that you can make a tax-free profit, is NOT A GOOD STRATEGY!

Having confidence in your ability to evaluate the deal and that your numbers are accurate? 

Do I have a legal duty to review my ads to ensure that they are accurate?

In a multi family property, you may add up to 2 quantity ADU units to the existing multi family lot.Any and all ADU's can only be up to 1200 SF - that part is accurate except for the junior ADU which maxes out at 500 SF

I suggest updating your time log accurately and ensuring compliance as best as possible!

AirDna seems to be the goto place for rather accurate data.My STR on Dauphin Island generates about 50k yearly. 

Be sure to include information about nearby attractions, public transportation, and local schools.Accurate information: Ensure that all information provided in your listing is accurate and up-to-date, including the rental price, property details, and availability.Timely updates: Keep your listing updated with any changes in availability, pricing, or property information.