pet rescue land

this may have already been posted but I can't seem to find a search button. ? we want to start a pet rescue, sanctuary, Sonny's Ranch. we're just starting out trying to get donors, etc. how much land would we need? my husband has a lot of experience with pet rescue, I have nonprofit experience but some of the operation stuff not sure about. I'm guessing 3 to 5 acres? since we'll probably have mostly pits, they'll need room and a facility and a small office, and a trailer on land for us. experience anyone?