A backyard garden
It offers a lot of exercise for the one who is doing it, it provides you with your own food, you do not have to go into mainstream farming where one has to buy land and employ farmhands. The food being cultivated can be made organic and offers you protection against what you buy from unknown sources from the open market.
These days other types of backyard gardening are being introduced, using Greenhouse technologies and aquaponics. This is not to say that these technologies are restricted to backyard gardening as many commercial farms are using these methods. If you are an Agriculture enthusiast it is one way to practice your passion.