Guys this is so easy to do and is so rewarding. All you have to do is pick up materials at the location that you farm things and the materials that you get for building in houses sells for 600 each. A stack is worth precisely 120k but if you want it to sell quickly then only sell stacks of 20 at a time for 12k a piece, and I can guarantee that you will make 200k per hour. On my platform they go for 600 a piece and I play on PS4, I don't know about PC or XBOX but I can safely assume that it is around the same amount.