Check your local zoning first, of course.
Then check out Cherry Hill's Horsekeeping on a Small Acreage from the library or buy a copy from Amazon, it will answer most of your questions.
My general rule of thumb is that the smaller the acreage, the more labor intensive and more expensive it will be to keep horses on it. Keeping a horse in a 3/4 acre paddock may actually be more expensive that boarding at a place that has decent grass.
You will have to pick that paddock every day, as well as muck the stall, and you'll have to have a plan for disposing of the manure. You'll also need a place to store hay, bedding and feed.
And think about where you're going to ride - is there room for a ring or a round pen in that set up? What's the drainage like? After the grass is gone, will the footing allow to ride, or will it turn into a mud bog?