I built a trailer to put my 1969 Avion camper on. I then had to rebuild the camper. For me, building the trailer was the easy part. It was about 3 weeks of work if I had all the parts available at the time. I built it to do what I wanted it to. There was noting available that would meet my specs.
I now have a 19.5' trailer that holds one quad, 80 gallons of water, 100# of propane, 20 gallons of gasoline and has a 20 gallon black water tank and a 20 gallon gray water tank. It also has room for another 30 gallons of water. It has solar and has been from AZ to northern MT three times and all over AZ. My 34' Avion triple axle trailer never gets used anymore.
Building your own has it's advantages, but mine still took over $15,000 to complete and I already had the camper. I have $6,000 in just the trailer assembly. If you don't count the value of your time, and you have the skills, you can end up with a nice rig. Don't expect to get the value of your time out of it when you are done with it.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25053498/srt/pa/pging/1/page/85.cfm
