Excellent advice so far. $12K budget, Queen bed, BBQ competition 1/2 ton tow rig...makes me think you will soon be disappointed with whatever you buy new.
If you are handy/crafty at all consider buying a new cargo trailer and converting it to your needs. Strong, (walls and roof made from welded 1" steel instead of wood or fiberglass laminate. Low cost, barn doors or ramp door at back, Queen bed no problem, plus room for your BBQ gear.
We did ours as an outdoor adventure toy hauler camper, since nothing in the market met our needs and price point. (Mine is listed under No David! on the Cargo Trailer Conversions sub-forum)
Examples here:
notes for the Cargo Conversion beginnerMore here:
Cargo Conversion examples Sky is the limit on layout, and type of fixtures, cost is determined by you. Time might be an issue, based on your immediate needs and build out requirements. I had the factory install my windows and RV door with screen and single step along with 4 stab jacks at the corners, I did the rest, electrical, insulation, E-track, etc. It has really been fun, and when camping folks often ask for a "tour" and "say it's really all you need, or wish we'd have done that."
Here's a cargo trailer with a back porch. You could do build your living quarters up front, BBQ compete on the back porch!
Cargo porch trailerGood Luck!