The most difficult and labor-intensive part of any Tiny Home build is the shell on the trailer. This can seem overwhelming to a lot of people. One option is to have the shell built to RVIA standards and then you finish the inside as time and budget allow. Here are a few links to companies that offer this service. This is not an endorsement of their products and I am sure there are other companies that can offer similar products:
When you think about it, all you really need is a weathertight shell, a completed bathroom, and electricity. Then, you can finish the inside as quickly or as slowly as you like.
You really can do this.