I think it depends on what state you live in as far as legalities go. I think in my state it's 3 acres for the ffirst horse and 1 for each additional horse. So it would be 8 for 6. BUT, if you have a barn and each horse has a stall that it is assigned to then you don't have to have quite as many. But that is assuming you feed hay AND grain to each horse.
Farmpony what state are you in that the law makes them have so much land? Here its up to each county and town as far as min. Amount. For instance in the farm area they require more land then say in St Paul. 3 acres for a horse and there would be 1000's in this state with no home. Theres boarding stables in the Twin Cities area with 5o head on on 10 acres.