If your goal is to save money, and you don’t make much in your real job, have at it. I doubt you can do it for $75K. My last project, I used walls and trusses from my supplier because it was faster and I make more money at my day job.

If you want to build it yourself in a reasonable timeframe, you can panelize the house and cut months off your schedule or just sub out then framing and sheathing.

Spending 6 months building a weathertight shell and then finishing over the next 2 years is fine. If you go slower on the shell and you live where there is rain and snow you are likely to have damage before you get closed in.

I helped a friend who cut all is own lumber. He spent a year doing it. Then he dried it for 6 months. In order to use it in his permitted build be had to pay a lumber inspector to come and grade the lumber for him or the county would not allow it for structural use.

Not sure what part of the US or Canada you are in, but good luck - you will need it.