You are a bit late for grazing as lets normally run from April to November, but i would guess about 100-200 pounds, as the grass is rough some people might not touch it as it will be mostly winter kill and will not give much goodness to the sheep equals less growth. As for the fencing idea look at the rent cost, it does not add up for someone. if your paddock was fenced and in good nick you could ask more, about 500 for a season.
Also dont waste your time and money on electric fencing as most sheep will just walk stright through it. You need stock netting and single string.
Hope that helps point you in the right direction.