Follow the guidance already provided.
None of the following should be considered legal advise.
I'm not an attorney, nor do a play one on TV.
For legal advise you MUST contact an attorney licensed in Texas.
Make certain nothing is received through the mail that has your guest name and your address on it.
Put a lock on the mailbox or a hold at the post office. You REALLY need to see everything that arrives FIRST! When mail is received with the guest name and your address, you are in deeper trouble. A skilled squatter knows this.
If you do not follow the legal process, and choose to box the stuff and put on curb, and change the locks, and as a result your guest encounters some harm, your deep troubles turn into unimaginable troubles.
Proceed with caution.
Packing the stuff and placing the boxes on the bed upon which sleep occurs might communicate your wishes clearly. REPEAT the Process daily. Try to regain possession of THAT key.
You may find it necessary/beneficial to invite a "witness" who has known you a while, to visit you for a season, before the show starts.Make sure they are aware of potential hostility. That is why we all rely on BIG Brothers!
Unfortunately, it is most likely there will be an attorney in your future. Now is a good time to start collecting references.Your REALTOR may have an attorney to direct you towards.