Is it ok to use 4x6x12 posts 2 feet in the ground?


Your posts is what keep the building from blowing away in a wind storm. If
you live where there's no hurricanes, tornados, or severe thunderstorms you
might be OK. For my barn, the posts are four feet deep with a 12" concrete
cookie for the posts to rest on. The cookie has rebars in it that are
stapled down to the posts. The cookie will cost you $10 a pole extra, but
now the weak link is the building shaking apart, not coming out of the
ground.

There's tons of places that offer complete building kits. Much better than
buying the parts al la carte. Nearly every lumber yard and big box home
supply around offers a kit.

Karl