The age old argument about is there money in the Federation?
Even if there's no money in the Federation, Voyager's economy runs on replicator rations.
They're communists, so even Suder locked in his room, or the Equinox 5 slave labour gets the same ration as Janeway.
Do the kids get the same replicator ration as the adults?
Baby Naomi, get's the same replicator ration as a full sized adult.
You don't pay for food in the mess.
You don't pay for your room or air.
You don't pay for holodeck time, but then again Holodeck time is probably rationed out evenly... Which means there just be a conversion table for holodeck time to raplicator rations to holodeck time.
Chakotay got Tom (squint) kicked off the ship for gambling with Replicator rations, yet even Janeway was gambling with replicator rations over the babies sex (due date?) by year seven.
So the black market is a gray area.
Childcare is one of the only few possible legal revenue streams on Voyager.
Before, I've always said that Sam Wildman and Neelix were doing it.
But maybe hey weren't?
Maybe it's that everyone else on the ship didn't understand money and found that working for "money" was a little distatseful, and that they would, if they were going to look after the kid, rather volunteer their time for free, which they don't really feel like doing.
It's like when you look after your brothers kids.
It costs 40 to 80 dollars per head to look after them in an interesting meangful way, going somewhere fun, but you're a jerk if you don't foot the bill yourself, so you don't take them out as often as you should.
Neelix was the only person skeevy enough on board to take money from a baby.