I've read several different pieces of advice on how to make money early in the game. All of them mention obtaining lock picks and robbing houses. I've yet to find any children to trade with and the few merchants I've found didn't offer them for sale. Can anyone give me a sure way to obtain them?

Gryph sells lockpicks. The children only come out to play after 9 am or so, be patient. The girls trade lockpicks, so make sure you have a bunch of jewelry and/or needles to trade, they're expensive. If you break into houses, you'll find children there as well, but do your trading before you loot.

I should mention that it's unnecessary to rob houses to beat the game, but if you want to do so, go ahead of course

Where do I find Gryph?

Nevermind, he's labeled on the maps. Much thanks.

I only had to break into a house once, and that was late in the game when I was too low on health and ammo to risk entering an unlocked house that might have marauders in it. My advice to you if you decide to do this on Day 1 is - be very, very careful.