Look at craigs list for used towing stuff. $1000 systems often are found for $250 or less. Biggest thing is what do you want for a brake system. Many are the PIA add a brake which means every time you want to use the truck you need to pull and store the brake system. Then when ready to tow re-install.
I use the SMI system, built in, flick a switch and its ready to go and runs off tow vehicle brake light system. There are other similar out there. Make sure you have good tow chains/cables capable of handling the truck if it should ever come loose.
here is what I mean 1 local to you other to me.
http://oklahomacity.craigslist.org/search/rva?query=brake+systems
http://tucson.craigslist.org/rvs/5069646045.html This is what I have