sound advice above, just to add
i ferret twice a week from august to march and my land consists of a livery stables, a farm owned for a ladies horses , a goat farm, a large garden on a country house, and a small sheep farm (although he no longer owns any sheep and just rents the grazing) and a couple of fields around a builders yard (i also have shooting rights on 3 of those above)
my ferreting partner has permission on an allotment area and a private school grounds....as you can see i dont spend long on farms or with farmers but have lots of land to keep me going, and my average catch