Denny,
I recommend starting with freehand hollowing then if you catch the bug and want to hollow large things move to a captive system.
It can be cheaper to go freehand and hollowing can be done on a smaller lathe than needed for a captive hollower. I have the John Jordan hollowing bars (the other JJ, may he rest in peace), handles, and arm brace handle. These will easy hollow moderate sized forms. I also use some of the Hunter tools for hollowing and have some mini hollowing tools for small things like ornaments. Look here under Tools for the Jordan tools.
Turned and Carved Hollow Vessel
www.johnjordanwoodturning.com
If not aware, there is a simple way to easily hollow deep things taught by several (Jake Niedling did a demo on this recently in the Knoxville club). Shape the outside of the piece, part it somewhere in the middle, hollow both halves from the middle, make joints on both halve just as you would a lidded box, glue the halves together, and use some means to hide the joint if desired. A lot of people in the club who had never hollowed anything successfully made hollow forms on the first try.
For urns, Niles bottle stoppers sells some threaded bronze rings that will let the lid be fastened securely and still come off easily.
JKJ