mlts22 wrote:
If the trailer is going to be somewhere permanent, and you can get sewer/water/electric, I'd also second the park model recommendation. Those have no tanks, and are more intended to be mini mobile homes, as opposed to travel trailers that move more often.
If you want good quality, check with a horse trailer maker. They can do top tier custom work... but you will be paying for it.
A lot of park models have holding tanks. Looking at Ceder Creek Cottage for my seasonal site. If you want the best I would say New Horizon, Excel or Continental but would be hard to find used.