Welcome to the insanity.

I started building my Teardrop right after Christmas. It's going to be a 5 x 8 Benroy style Teardrop. I not a woodworker by any stretch on the imagination, but I enjoy tinkering with all sorts of things. If you are anything like me then building your tear will be......fun, frustrating, a learning experience and a great way to make new friends. Jump in and have a blast.
I'll throw my 2 cents in on your questions
1.) Do you have to register a tear in Utah ? Here's what I've found out... In Utah, a single axle trailer under 750 lbs does not have to be registered. If you take it out of state, then you might have issues. That being said there are several people here who travel a lot and have never had a problem. I had my trailer frame built and I have paperwork that states it is a utility trailer complete with a VIN. I called the DMV to ask about registration. Neither office I called had a clue what a teardrop trailer was. I told them it was a utility trailer with a box on it that I can sleep in and has storage space for supplies. The first office I called said to register it as a utility trailer for $70 (reg + tag) and it would be good in all 50 states. The second office said "Oh you can sleep inside it, so it's a TRAVEL TRAILER. That'll be about $230 a year".
2.) What should I be paying ? All I can tell you is I've got $1400 tied up in the frame, materials and hardware. I'm guessing that we'll be closer to $2000 (or more) by the time we're done.
3.) Any suppliers in Utah if I should have to build. (aluminum, dead-soft T , handles ect.) ? I haven't had great luck with that. I got most of my hardware on-line. Best Way Trailer (801-268-1412, open Mon thru Fri) in SLC sells a variety of aluminum trim. Many of the big RV places buy their trim from these guys. I just bought some 1" x 3/8" aluminum corner molding to use for roof edge trim in 16 ft lengths.