A few years ago I ran into a book specifically on this subject; it would behoove you to have your library dig it up.
I'm involved with local planning/zoning; I would be surprised if there were specific ordinances for tennis courts. The chief concern would be drainage; you may have to keep it a few feet from your neighbor's lot line. It would probably be treated like a patio or driveway. You would likely find an increase in your property insurance cost; people may trip and fall, etc.
With respect to raising the value of your property, I much doubt it. It would actually eliminate a good many prospective buyers, and even tennis players may not wish a large chunk of the lot taken over for this purpose. . . but then, you may be in a part of the country where this concern would not exist.
To Praise, To Bless, To Preach--the Dominican Order