In TX you can pretty much get unlimited number of tags for your property that you own or hunt ont. You need a management plan in place and approved by the state - and a biologist will help you if you don't know how to do one. Once in place you get tags, in some cases extended seasons, movement of season within a framework etc...
It provides for a landowner, hunter or leasholder to manage a parcel of land (harvest enough deer) without having to resort to bringing in day hunters to kill off enough deer every year. It doesn't have to be a landowner. A group of guys who have a lease can get a management plan in place and get on the program and get additional tags as well. Lots of leases are on these, not just in South, TX on the big money places but the cheap East, TX leases as well.
When you own 4,000 acres and have a healthy deer herd with a deer for every 7 acres you aren't going to bring in enough hunters to keep them in check even if you wanted to (and who does).
There's a fee involved with the state and you have to keep records and renew your plan, provide harvest date, do spotlight/camera surveys etc...but it's not hard and like I said you can get a state biologist to help you out.
I own 50% of a pretty good chunk of land in TX with my sister as my partner. I manage the timber and the wildlife and with my wildlife management background I do the management plan. The tags can be filled by anyone with a valid TX hunting license.
Here's the offical FAQ on it from the TPWD site.
Q4: What is a MLD Permit and how can I get one?
A4: An MLD is a Managed Land Deer Permit. These permits allow hunters to take additional deer to better control and manage their deer herd. There are three levels of MLDs. The first, a MLD Level 1 allows the harvest of antlerless deer. A MLD 2 allows the take of both antlerless deer and spike bucks. A MLD 3 allows the harvest of antlerless and any size buck deer. To obtain this permit one needs to talk to their county Wildlife Biologist. The Biologist's names and phone numbers can be obtained by calling us or by going to the website: Land & Water - Find a Biologist - and clicking on your specific county.