I am wanting to build an extra garage because mine is full. I am
thinking of building a pole barn type with 2 garage doors. Probably
30x30.

I have been fighting with the idea of building it myself. I have a
tractor with a bucket available to me as well as an auger for the
tractor.

Any advice? How far are posts, trusses spaced? How do I ensure the
building is square?