What I want, I tried to make in my drawings, I hope everything is clearly visible, and you'll have enough informations to build your own "dream tiny
house". In the meanwhile, I would like to point on following:

A. Bill, the most important, ussually. I can gaurantee for the bill with tolerance of 20%.
You can make almost all of the wooden equipment by your own, to make your bill the lowest possible.
Also, buying in local neighbourhood market is always a good idea.

B. Measurments. As you live in US, I used feets, but, in some less important drawings I used meteres. That is not issue at all, as this
refers to furnitures, so can make according to yours.

C. Surface net, is about 400sq ft, which is pretty lower than 500sq ft.
Why I did like this, to waste 100sq ft? Simple, I am not shore for the way your local gov count net surface.
In the case, you are on the safe side, you can just add more extra space for you, and to have whole 500 sq ft.
You'll see in the floor plan about this, in is not so complicated as it maybe looks like.

So, that's all, I guess, I hope you'll like it and enjoy in your tiny house!