Look for used Simplicity Tractor dis(-)s or cub cadet, I found two sets of them (free) and rigged them together to make a tandem set to pull behing my atv. I tried to make them oppose each other like a commercial set and this did not work, it just danced back and forth even with the weight. I guess they are three feet wide.
It is not the best thing on the market but it sort of works alright, I placed a solid concrete block on top of each section to weigh it down.
I think a set of harrows would be better than these are to till up ground.