Considering converting cargo trailer to RV - need advice

During the last recession a lot of consruction workers started modifying their utility trailers for trips away from home. Most are fairly primitive. Utility trailers are poorly insulated and have few windows. They are hard to heat and cool. They are close to the ground with little room underneath for tanks.

For what it costs to put one together you can find a lot of used trailer for the same money or much less.