I do start the potty training here. My thoughts are: a child spends most of the day here so it is easy for me to start them sooner. Children are fully trained by two and two and a half. I only use diapers not cloth diapers or training pants that look and are diapers and i use ikea potties.
My approach is same as in a centre we do it as a routine. I have 5 potties and the toilet with the child seat included. Everyone sits at the same time even babies (only if they want to) I keep a stash of bathroom books; we sing at least three songs there wash hands etc. (Creating a positive experience helps to potty train sooner) I had children potty trained by routine at 16 months and as soon as they develop language and fine motor skills they're fully trained and transitioned to cloth training undies (Walmart). My children love our bathroom time.
I know, many think it is training the adult but, in my case it makes my days go absolutely smooth when I only have to deal with one or max two babies in diapers and the rest is trained.
Parents are very appreciative and they follow the lead. Also I had clients coming here with older children that didn't get potty trained in other daycares I do not promise anything but in a matter of three days their children were trained. No rewards, no celebrations just love and patience. Now, I absolutely do not advertise my services as potty trainer because every child is different and every body functions differently, I only create a pleasant experience and that's it. And parents can not believe on how easy it gets for them when their young children are trained earlier (thats another reason I also do not sell the idea of cloth diapers, in my group all get trained sooner). During summer I just carry one or two potties and still continue with our busy days.