I purchased my home (with 2 acres, approx 80,000 sq. ft. of land attached) because I knew I would build a dojo...someday.
After the storm of the century blew through and felled trees and out buildings I was standing in my back yard when I heard a voice say "If you build it, they will come."
It wasn't my VCR on overdrive, it was Dennis Hooker, my closest friend. We got out a 100 foot tape and some stakes and layed it out on the spot.
That was twelve years ago. The students came. I have offered the as-builts and engineered drawings for free to anyone who would like to re-create this dojo. Several have. They are still available somehwere in my cluttered office.
It takes commiting a moment, no more. Just don't think about where the money will come from or if you will succeed or fail. If you are a Sensei, and no one can determine that but you, you must take the first step and then proceed, no matter what. I've seen great dojos rise in surprising places and seen what should have been great dojos fall from surprising heights. Just go forward and believe. Think of all the fun and profit just out there in front of that rainbow...