6-months is supposedly the minimum but I've seen 1-year be recommended. As for moving gyms, you are applying based on the credentials/certification of the gym who say you have signed up with. I guess you could sign up for two gyms for 6-months each and submit the paperwork for both at the same time with a cover letter explainig your one year plan. Now that I say it, I guess you could do that with 3 months at two different gyms, but I have a feeling they wouldn't like that.