Nala -
The public land permit is $48 on top of your license fee.
I recommend downloading and reading this book cover to cover:
http://www.tpwd.state.tx.us/huntwild/hunt/public/lands/table_contents/media/pwd_bk_w7000_0112a.pdf <-- this is a 48 meg file, it's gonna take a minute to load the page
It outlines what can be hunted, when and where.
There are also maps of the areas, and now with the addition of Google Earth and Bing Earth, you can get a pretty good feel for the area before heading out.
As for day leases, I've not hunted them very much. I've seen day leases go from $75 on up to $400 per day for hog hunting. There are plenty of ranches offering package deals with an exotic and a couple of hogs for a reasonable rate as well.
I've always had family land and/or a year round lease. I've also traded hunts and done labor swaps in exchange for hunting privileges: I'm an electrician by trade, so I've wired a few barns and camp shacks; I've also built a lot of fence, hauled stock, run tractor, done some welding, car repair, pulled weeds and other things in exchange. The barter system is alive and well.
Hope this helps!