Sunlight, soil and slope is more important than size, particularly if you stay away from field crops, corn, and orcharding. We're on a generous 1/3rd of an acre, say 15,000 sq ft, with a big-ass house, a lawn (more than I'd like, actually), greenhouse, chicken coop, lots of storage space, a shed, a dedicated "patio" type space....If anything it's too big. The heart of the garden is 18 4x8 raised beds and we pretty much only occasionally buy carrots or onions if I've not grown enough, plus tomatoes and bulk fruit for canning. Everything else that's a vegetables and much of what is a fruit comes from our garden and we are big fruit and veg eaters. So I think 8,000-12,000 is a great amount of space unless you want actual self sufficiency in grains and meat too. Your time at that size will probably limit you more than sq. ft.