PH, it's legal to commercially fish with a trotline for certain freshwater catfish. I have no idea what the licensing requirements are, but, from the Texas commercial fishing regulations book:
NONGAME fish, channel catfish and blue
catfish may be taken by trotline.
For trotlines fished under a commercial
license, flathead catfish may not be
retained or possessed.https://tpwd.texas.gov/publications/pwdpubs/media/pwd_bk_v3400_0074.pdf
Not a clue what the going market rate is or how much is a 'good' haul.
"Decency is not news; it is buried in the obituaries --but it is a force stronger than crime" ~ Robert A. Heinlein, 1952
I can't give legal advice yet, but this site may have some of the answers you need: https://texaslawhelp.org/