Not sure where you live but if it is near a big city, you would have less travel. My DS modeled when he was younger, mostly print ads for Gap (they do these in NYC, gap.com shoots in CA), Pottery Barn, Hartstrings, Fisher Price and a couple of other local places.
You can go about it in a couple of different ways, calling companies yourself & finding out if they are doing casting calls, etc.. or going thru an agency (who would not charge you) and having them call you with work. We started out on our own and then worked with an agency when he was over a year old.
You can do your own shots, most places like to see some good head shots and also full body, depending on what they would be modeling. Black and white exposure are good to have along with a few color shots too. If you aren't good at taking pictures, ask your friends, neighbors, or relatives if you know someone else might do a better job.
Good luck!