A medium sized monitor or inexpensive to feed? Seriously, you don't even have the monitor yet, and you are already looking at cutting corners. It's not that feeding monitors is all that expensive, but that combined with enclosures, vet bills, and electricity does add up.
I would always recommend avoiding any w.c./import monitors, they can be a touch more complicated than the c.b. species.
Medium sized monitors that are available c.b., fun and not shy, goulds and on the larger side argus (there are also flavis, two ways, and three way crosses, but I don't have these). Both of them are mouse vacuums though.
If you don't have them yet, and are concerned about money, you'd probably be best served avoiding monitors entirely.
--Robert