I much prefer to start them as young as possible as they adjust more quickly and learn your way of doing things (rules, routines, food, etc). Even a 2 or 3 year old might cry a lot in the first days depending on personality. I have a 9 month old who started last month and has never cried...just smiles and sleeps...he's a dream. It depends a lot on the child, not the age. I had an almost 2 year old come for a half day on a drop-in basis last month and he cried to the point of vomiting for the entire morning...and he was strong and resisted getting into the car seat when we went to pick up my son from preschool...it was not a pretty sight. I'd be willing to bet that the little one you just took on will stop crying after about a week or so. It is normal. It will pass and then you will have a very well-adjusted child.