There are many, many different potty training approaches. Before you decide that they are "too young for potty training," you need to know what the parents have in mind.
My preferred approach is to be very gradual. I start out with kids as young as 12 months or so by having them sit on the potty fully dressed, then transition to sitting on the potty before bath, or at diaper changes, with a naked bottom. Hopefully before too long they will tinkle a little in there, and you can get really excited about it, heap on praise, etc. in hopes that they will try to pee again. Before too long, they should make the connection: potty=pee.
Once they can void their bladder intentionally, start going an hour or two at home with undies on, but no pants. Take them potty every 30-45 minutes, give them lots of water, and plan for some accidents. Do this as often as possible (between afternoon nap and dinner is a good time, IME). When they can consistently go 1 hour dry, you are ready to try leaving the house. Go somewhere kid friendly, pee before you leave, when you get there, before leaving the activity, and as soon as you get home. As you go along, they will be able to go longer stretches between visits.
There will usually be some one-step-forward-one-step-back, as you go back a phase in response to accidents, but this is the progression I typically use. The "potty-trained in one weekend!" approaches typically only work for older kids, and even then, it can be too much pressure. The benefit of having a nanny is being able to makes these kind of changes gently and gradually.