You would have ongoing filing requirements with the State and would need to keep business records and documentation.

My goal is to buy one rental per year with price between 150k-250k for the next ten years (if i get to keep my job). 

Great job! 

I have been able to find a couple of options for this setup though, they just require separate leases for each room and sometimes 2-3 months of rental receipts as well. 

My experience has been that although I outline the requirements for tenancy in my properties, both brokers and PMs still send people who would qualify for most property owners but do not meet my outlined criteria; and then are SHOCKED when I reject them.  

I did do a precursory investigation into what requirements are and it looks like there might be some zoning restrictions, as well as permits required.

The macroeconomics are on fire here - population growth, job growth, and companies moving and developing here.

The bathrooms are very narrow so I was wondering if there's a requirement to have a bathtub.

In Texas, as a licensed agent, you’re generally required to use TREC-approved forms for real estate transactions unless an exception applies, like (I believe) leases longer than 1 year or where no TREC form exists.

Even a single family builds can vary significantly based on site conditions and required structure/design.