Purchasing frozen rodents in bulk is, in my mind, the easiest means of feeding a large specimen. I use this term literally - I have minimal time to spend with my animals due to work/school, and its simply more convenient (and infact, cost effective) to use frozen feeders.
Sure, you CAN breed rodents and such (and may well save/make some money in the process!), but reality is that you still have to feed your feeders, have to take the time to care for them, have to worry about various issues of cleanliness (smell, wife-factor, and child-factor if you have them; plus various environmental issues depending on where you live)...blah blah blah.
Long story short: Which is more valuable to you - time or money?
If youre short on time - go with frozen rodents.
Can buy them in bulk, and if you shop carefully you can usually find some really nice deals (especially on larger items, like jumbo rats/mice). I also mix in baby chicks/quail, which my animal loves (especially the quail). Throw em in the freezer, tell your wife to suck it up (if she cant deal with a few mice in the freezer, hows she gonna handle a large possibly-aggressive lizard?), and youre all set. I typically spend approx. $200 for a 6-8 month supply of rodents/birds; which really isnt a big hassel for me personally.
If youre short on money - go about setting up a feeder group. Depending on whether or not you plan to have more than one of these animals, a rather small feeder colony could serve your purposes well. If you plan on feeding a colony of monitors though, Id personally go with the frozen - less time spent worrying about feeder mice, more time spent enjoying your animal(s).
Then again, Ive also not had much success with feeder breeding. If you DO go that route, I would definitely suggest using rats over mice. Aside from the obvious 'more meat' aspect, rats are also (im told) less likely to become aggressive towards cage mates.
As someone mentioned above, hunters should be your new best friend - you might even consider looking up the local game butcher, who may well be able to provide scraps.
Other businesses Ive heard of people obtaining cheap feed from:
- chicken/duck farms
- rabbit farms
- fish markets
- butchers
- the road (I know of people who have little issue making use of a freshly road-killed deer - better than leaving it to rot and can provide a massive quantity of meat if you have the refridgeration space to keep it fresh)
Depending on just how large a species youre talking, you may also want to consider a colony of roaches. While your wife may not like the sound of that (could always post something like this in the basement/toolshed/garage), it could serve as a nice addition to your animals' diet - both large and small. It should also reduce your costs to some degree.