I agree with what everyone posted. I have a small light trailer now with an RTT. I just started a tear drop (sort of) build. I've had the small one for a couple of decades. It's been great but, now I want a little more comfort.
@RoyB built one from a Lowes platform, some people start with a Harbor Freight frame (too light duty for me) or a small box trailer and add in windows and interior. Mine started its life as an M100.
My new build started on paper almost a year ago. I've built different trailers but never an enclosed one. So yeah, read build threads. If your not sure which way to go, rent something and see how you like it. My original trailer has been to the Rubicon, Dusy as well as just camping in the desert. My new one will not be that hard core.