Andy,
If you did it, why would you build a real green? It would suck to actually putt on thanks to all the ball marks. Just mow an area lower and call it the green, and if you really have to have a putting green put it elsewhere. I'd sure use artificial turf of some sort before I'd have something as expensive to maintain. What if you go on vacation for three weeks? Its one thing getting a neighbor to feed your cat, its quite another to get a neighbor to mow your putting green every day unless you let him use it whenever he wants!
I think the best deal is just to live next to a green so you can use it as your private putting green without incurring any of the expense to maintain it. Preferably on a course that's not really busy so you can actually use it, and won't chase you off if they catch you there. And most definitely with your house not so close that it is at risk from errant shots!
Maybe I'm a little nuts, but in the house I'm planning to build, I'm going to sink a 4" section of PVC pipe in the basement slab (i.e., glued down onto the slab insulation before the concrete is poured) in an area I'm going to carpet. When the carpet is laid that circle can be cut out and glued onto a piece of wood that'll fit in the hole so it isn't a trip hazard, but I can use it for winter putting if I get the urge. Not that I ever do any winter putting now and I have a basement with carpet that would work for a putting green -- but maybe its because there's no hole! And yes, I know a hole is 4 1/4" and not 3 7/8", but I figure a slightly smaller target will make the hole look bigger come spring and 4 1/4" interior diameter pipe is probably harder to find
