How much land do you have? Agreed with Sour, that checking with your zoning laws would be the first step. Just something to keep in mind: If you make a tractor, it will need to be moved every day in order to keep your birds from destroying the lawn under it. Tractors that are truly mobile are also difficult to make predator proof. Even in the city, you will have possums, coons, rats, snakes, and even weasels. And if you ever intend to use any chemical insecticides/herbicides you won't want your tractor on a treated lawn.
I would opt for a small flock in a well designed stationary coop/run. I would avoid the prefabs, and design a coop that compliments the style of my house. It would be a walk in, with attached walk in run. You could soften the visual impact by putting a flower bed or a hedge of sorts around it. And, you might consider making a shed, with the coop being part of the shed. Every home owner needs storage for outside equipment. If your home has a garage, you could add on to one side or end of the garage.
Keep the following needs in mind: 4 s.f. in coop, 10 s.f. in run per bird. 1 l.f. of perch per bird, with perch being above nest boxes, at least 2' off floor, 12 - 15" from back wall, and minimum of 18" between perch and ceiling. 1 s.f. of ventilation per bird, or ventilation = to 10% of floor space.
