I'm a strong believer in dry firing. I'd not buy a special gun, but just use the gun I planned to use. Just make sure it is adviseable to dry fire the gun you have chosen. Most will not be hurt at all, but it is not a good idea with some models. Check first.
Some guys seem to think dry firing will hurt a gun. It won't hurt most of them any more than live firing, but remember this. You may have a gun with only a few hundred rounds through it, but it may have been dry fired 20,000 times or more. Your gun really has the net effect of having 20,000+ rounds through it and it has more wear on it than you may realize.
Not that that is a bad thing. Those 20,000 dry firings have made you a MUCH better shot. You may well wear out the gun by now, but how much would 20,000 rounds of ammo cost. Much more than the gun.