On another post within this forum someone was building a personal trailer by starting with just a metal frame, but this thing was going to be larger than what can be towed by a small car.
I don't think just any car can tow a trailer so find out if your vehicle has a tow rating and start with that. The tow rating will have to include the weight of the constructed trailer and the hitch hardware to tow it.
I have heard of others building their own, and there is certainly a love for teardrops, but you might have to search for a forum specific to this kind of craftsmanship. If you end up pursuing this, we would certainly like to see the results.
Well the ones I saw can actually be towed by motorcycles, so they are super light, depending on the frame you get I suppose... I essentially just want a glorified tent on wheels... nothing fancy... I take a lot of camping road trips and it would be nice to have something like that... keep your eyes open.. I'll pass it along if I ever do it