Texas is completely unique when it comes to relics, digging, land use, etc. What's normal there can be completely shocking to others. You won't be the first person to be taken aback by a Texas sifter dig, and the arguments rarely solve anything.
Pay Digs? Yes, lots of collectors build collections that way. There are a couple of guys who's full time job is finding decent sites, securing a lease, and running digs.
Leasing land to dig for relics? Yes, most of Texas is privately owned, and leases for hunting, digging, etc are all common land uses.
Legal to dig? Yes, Texas has laws lean towards protecting the land owners rights, and if you are the land owner or you have their permission you can do things there that are simply not allowed in many other states. Actually, many Texas based Archaeologists are the friendliest to collectors because they don't freak out that you picked up a rock and have a collection.
Many sites in Central Texas are rock middens, and given the massive deposits of flint/chert, native people made and discarded a lot of tools. It's mind blowing.
Joshua