I've modeled most of my life. First and foremost..... NEVER pay any $$$ to anyone.
You can submit regular snapshots to reputable agencies and if they like you, they will contact you. You do not need a portfolio unless you are contracted and that is later on.
Next... This is WORK. Not all fun and games. Be ready for a LOT of rejection and have a thick skin. Casting calls demand that you bs there when they say which can be in the midst of mealtime, naptime etc. You are "on" when you are on... Thats it, even for a moody toddler/baby.
IF you do get hired, put all $$ into that child's account.. That child is working. If the child does not like it, please don't live out your dreams... Stop it.
My 16 yr old models as well. We came home when she was 10 from a shoot in LA and she said "I'm done". That was it. I never mentioned it again. She has since picked it back up.
Only deal with reputable agencies. I don't know local good agencies in your area. In our area, the Campbell agency and Kim Dawson are good.
You are not reimbursed for your travel time and time spent ( lots) waiting unless it is in a contract.
Be careful, it is a very rewarding business but also can be a very mean business.
Good luck.