how much land do you have? we raised quite a lot of goats on about an acre or so of pasture growing up. i would think about an acre of pasture for one cow would probably be enough, especially if you supplement with hay. go to your library - they should have a book or two how to do it for the 4-H kids.
i would think that raising your own cow would be VERY cheap - especially if it's grassfed. we didn't have a lot of money growing up, but we managed to raise 100 chickens most summers & survived on that over the year. we couldn't have done it if it was expensive.