In a recent post the OP has declared that his home-built 28-foot trailer will have a resale value of $50,000. IMO, this is impossible, and the OP should do a hard reassessment of this project before he gets too far into it.
Based on the basic nature of the questions he is asking, it is unlikely that the trailer he is designing will appeal to anyone but himself. Not a problem as long as he is occupying it, but he should expect little or no resale value at end-of use.
Additionally, private RV parks that have a "ten-year rule" also prohibit any home-built RV, no matter what it looks like. The OP must factor this into his choice of campgrounds.
The question was asked previously: What is the expected weight of this trailer (and the tongue weight), and what does he expect to tow it with?