I kept geese for grass control in garden and farm access areas for a few years when I lived in Georgia (USA) I found them to be about the easiest critters to keep, very hardy, resourceful, self-sufficient. I would shut them in a tight pen at night to guard against predators (and produce wonderful
compost in the litter in the night pen--it naturally bred red compost worms in huge numbers!) The females would all lay eggs at about the same time, early in the spring, and after two or three days hatching each lot under it's own mama, all 5 to 10 mama geese would combine all the babies and raise them together.....a huge lesson in cooperative community! With that many watchful parents around, hardly a gosling got lost to any cause.....quite unlike ducklings, baby chicks, etc. (which all stay with their own mama only, and the small ones often get lost, get caught by the cats, etc...)
But this was on the farm. Geese in town are another matter. Here in the US both wild and feral geese are considered pests in places like public parks and golf courses, and great efforts are made to get rid of them from such places. The noise and manure produced by a number of geese living together can be prodigious and fresh goose droppings are long, green, and soft....both unlike and probably worse smelling than the small round pellets from sheep or goats. And geese can be quite aggressive toward people, small dogs, etc....especially if there are nests or babies in the mix. I can see you becoming quite unpopular if you turned a bunch of geese out somewhere in town, even with good fences and management, geese make NOISE.
The Muscovy duck is a possibility too. They graze like geese and are otherwise somewhat similar, except that they don't make noise....mostly they just make a nasty hiss. They, too, can be mean around their nests.
As far as marketing goes, I had gourmet restaurants in Atlanta paying me $1.00 US each for goose eggs, and they took all the eggs I could send them from ten or fifteen laying geese once I decided that was as many geese as I wanted to deal with. As for the old birds they went in the curry-pot, but then I maxed out at about 25 birds so there were never that many of those at any one time.....