Gary:
I'm not sure if I qualify to answer this question. I'm on build #3 which was a long time ago for some members here.
I'm one of those builders that believes the kitchen sink should be left in the kitchen (not a teardrop galley). Your goals are reasonable for a 4x8' 'drop. With your philosophy, and already owning the trailer, you'd be highly challenged to hit the $5G mark unless you want to do the gold-leaf sheathing option. Here's build #2:

It weighs 850 wet sitting on a light weight chassis. Without the chassis I spent $2640. That's with a Fantastic Fan and commercial doors.
I'm a big disciple of Steve Fredrick's Teardrop Shop Manual.
http://www.campingclassics.com/shopman05.html I can't begin to explain how much the 250 page document helped me. I'm on my third build and still reference it. He's a proponent of building a camper from "inside out." I really like his hatch construction method. I think it's a superior method of sealing and avoiding springback.
You can also download some side profile's off the design profile section:
http://www.angib.pwp.blueyonder.co.uk/t ... tear00.htmI bought my full sized profile from Frank Bear for $30 off of eBay for my 5x10.
http://www.ebay.com/itm/RV-TEARDROP-TRA ... 52&vxp=mtr The above photo of the 4x8 I built was developed from the design profile section. There's ways of projecting to a 4x8' sheet of plywood.
Enjoy your build,
Tony