You may want to visit with a counselor at a small business development center or a SCORE office in your area. Starting a shelter or transition housing involves a great amount of regulation at the local and state level. You will want to be certain you can meet the requirements before committing to a building. You may also want to look into what you would need to do to obtain payments from insurance, Medicare, and Medicaid, since some or all of them may pay for a vet to stay at your facility while waiting for permanent housing elsewhere.