IRS does not care. Texas Real Estate Commission cares.
If everything goes smoothly, nobody complains, then it is ok. The risk is, if there is any legal fight among tenant, property manager, and owner, the issue may get challenged.
It was one of the main reason for me to get a real estate license in the beginning. I started with real estate investment for myself, and did not want to get a license. But a few of my friends want to invest with me. I referred them to my agent and my agent helped them to buy rental properties. Since I manage my properties by myself, my friends want me to manage for them as well. I researched the issue and conclude if I want to do it legally, I must get a license.