Bev has talked about the idea of using a cargo trailer as a base for converting into a small tavel trailer and here is an example of just that on Ebay: item # 4513291200.
I'm not suggesting it's a great design, but it's always worth studying other people's ideas, I think.
Carson trailer of Bakersfield Ca makes a utility trailer that could be converted into a grasshoper type for 5x8 for $1595 comes with side doorand brake lights it can have brakes put in and mainy other addons for more you can choose the color you want 11 choices.
they sell a 4x8 utility trailer for $499
661-391-9805
and I would guess most states have a place that build work or play trailers for like costs.
...... Inside almost done--Trolly top has opening windows & roof.doors need assembling--pictured above waley windows..galley 1/3 done Cross Bow in Build Journals....http://www.tnttt.com/viewtopic.php?f=50&t=54108