I think better will be to create your own project with suitable design, and hire some company or special builders to implement it. I recommend to look here for modern models http://buildtiny.house/tiny-houses-for-sale-in-arizona-az/ this company offers factory prices and quick and easy delivery and installation. Try to contact them, they can make any project you want.
There is ways to build your own tiny house, me and my hubby have actually researched this. You can build a tiny house for as little as $1000 or buy one for as little as $6000 you can even find some community places where you can live in a small area with other tiny home owners. https://tinyhouselistings.com
Building a tiny house is not so different from building a house. Foundation, Framing, Plumbing, Electrical, etc. ....do you have experience in any of those things?
Building a mobile house is a bit different than a structure with foundation... But either way, you need experience, or to hire someone with experience.
If you want to DIY it (and you dont have construction experience): start with lots of research, expect it to take a lot longer, and expect to have to redo a lot.
I want to be encouraging, and believe that one can learn anything, but also warning that overall size, doesn't mean its any easier than building any other habitable structure.
The first thing you need, to start such a project, is good friends.
I fully encourage you to try new things, learn new things, and wish you success.
In hindsight, I should have been more helpful.
...thats what you were asking for, people with specific knowledge: so let me offer mine...
I am a former realtor, from a many generation builder family, currently working in custom bathroom design.
In my job I interact with a lot of DIY'ers, I meant to warn you of common pitfalls, but may have come off too discouraging.
Also, my Journeyman Industrial Roofer parent, happens to be building a tiny house for one of my sisters, at this time.
Though I dont claim to know much about that project myself.
My particular area of expertise is plumbing. Feel free to ask me about anything and everything plumbing, if I dont know the answer, I know someone who does.
The first thing you need to learn about plumbing is what type of pipe you need to use.
Its the newest best material, its lightweight (only thing used in mobile now days) , and its 1/2 the cost of anything else (go figure! the best stuff is also the cheapest stuff.)
The bonus of pex, especially if you are moving around in different climates, is that it can expand and contract, without becoming brittle.
i.e. If your pipes freeze, they wont burst. When they unfreeze, they will go back to normal.
Its a catch 22, if you dont know about a certain subject then you dont know what you need to ask....
Just tell me what you want to do, & i'll tell you everything i can.
Best of luck.