It might not be everyone's thing but have you perhaps looked at building a small poultry run for chickens? Perhaps sell the eggs or even buy in fertilised eggs, hatch them in an incubator and then sell them on gumtree once they are big enough? I know this idea probably wouldn't suit a vego or vegan but that's the first thing that came to my mind. You can get some really cool rare breeds of chicken as well (Plymouth Rocks are my favourite)!
Chicken poop is a really good fertiliser as well and also chickens are really good to have to peck around in an orchard!