barns cost 4 million to purchase then a extra 1 million to add the farming upgrade . then you have the ability to plant seeds either potatoes,weed,opium . you will need to purchase water and fertiliser from the farmers market . so for instance potatoes cost a outlay off 100k for seeds 150k for water barrel and 50k for fertiliser you get 1500 potatoes per bag of seed , they grow at a rate of 700 per 30 mins with the perk and sell for 1k per potato .