So far I have 207 hours on my build (I'm running a spreadsheet to keep track). That having been said, it's taken a year because I have a full time job & took 3-4 months off this winter from any work on it. I've probably spent five times that much time, at least, researching threads here online, to learn from what other people have done see some of their mistakes & problems.
I had most of the tools I needed already, but did get a couple of cordless tools as I went along. I was a cabinet maker for 25 years & have done some commercial, residential & aircraft work in a past life.
I have about $5,000 in materials so far (fully insulated walls, floor & roof), but I bought commercial doors, have a flat screen TV, voltage inverter, stove-oven combo, solar panel, propane setup & CD deck. I was lucky to find a used frame to start with (craigslist), & I would recommend that the longer you work on the build, the better the quality & the better the ideas will be. The worst thing for me would be to set unrealistic goals for time, then not be able to meet them & become frustrated. I have a job, I don't want the build to become another.
There are some incredibly helpful people here on the forum who are willing to share knowledge & ideas. A trailer is more than a thing, it's a dream & fantasy you can live. Do it!