I don't keep water monitors, but as no one seems to be answering your questions I'll see if I can be of help.
Water monitors can get huge and don't make an ideal first monitor if your current experience is with bearded dragons. You'll need to devote a spare room, or an enclosure of equal size, and keep it warm and humid. Most subspecies of water monitor get at least 6 feet in length or longer and will require a lot of food as well as space. There are no guarantees they will be calm, either, and have a nasty set of teeth.
If you want to try monitors for the first time, try one of the smaller species to start with, then work your way up. Ackies (Varanus acanthurus) are a good small, captive bred monitor. If you want something a bit larger, sand monitors (Varanus flavirufus) or gould's monitors (Varanus gouldii) are also good tempered and captive bred. You'll find that these are more expensive than water monitors, but will save you money on housing and food.
If you want more information on water monitors, go to the forums on cybersalvator.com (link attached to this message) as there are a few people there that keep them. If the link comes up with an error page, click on your browser's refresh button.
cybersalvator forums