I think you are being a bit unrealistic, to plan on building a "basic teardrop" in 2 weeks. Also, later in your post you feel that "3 to 4 weeks, 3 to 5 hours a day" might produce a campable teardrop with no frills. If all you are interested in is having a towable box that is somewhat waterproof that you can sleep in, I guess that would be possible.
However, most builders experience delays in their builds, due to time lost obtaining parts and materials, plus the complexity of the fit and finish of the final product. I know that this is what slows my builds down considerably. I am plagued by wanting all of the joints to be glued and screwed tightly together, then spending extra time rounding off corners, sanding off all of the saw marks and generally doing the kind of job that I won't be ashamed of when in a campground. Perhaps my 65 years of professional woodworking really isn't a plus when building a new trailer, and I find it hard to just slap it together, in an effort to beat the clock. Being retired, undoubtedly allows me to take as much time as necessary to attain the desired end result.
I have only built 4ft wides, and feel that going 5 ft wide and longer than 8 feet long, will also slow down your anticipated time of construction. I don't want to rain on your parade, but working part-time for a few weeks, might actually fall way short of your anticipated plans to really make it "campable". I agree that a few days spent altering a cargo trailer, would be so much quicker, but of course much more expensive.
For many of us, building a teardrop trailer is often a once-in-a-lifetime experience that will totally change our camping habits forever and puts us on a friendship level with other like-minded campers, that is unimaginable. I know you will also find this to be true, just you wait! Good luck on your build, take lots of pics, ask any questions and always know, we are here to help.

Roly ~~