Good morning and welcome....chickens are a good starting point with a small place...need a secure pen and shed for them, as suggested. I gather you're interested in a milk cow? With limited space for a cow, you might consider a Dexter (small breed for milk and beef), but you'll probably have to provide hay and grain year-round, especially if you are going to milk her. Before getting any cow, look at as many as you can before you purchase to get a view of what's available, pricing, temperament, health, etc. As far as a trailer, you might be able to find a used small horse trailer in good condition, which might be better than something home-made. A couple of suggestions: check around for local vet service before you get any large animal, just in case, cause sooner or later you will probably need a vet (do they make farm calls or do you have to transport the animal to them?). Your local extension service may be able to help you or refer you to sources regarding fencing, hay, etc. Are you "zoned" for farm animals? How close are your neighbors (chickens and even just one cow can make some noise).
Small or large, having your own space in the "country" is great. Just my thoughts on half a cup of coffee...not up to speed at this hour of the a.m.
Gale