If you go ahead make sure you have a VERY clear exit. A written agreement on termination should you feel the need. All may go smoothly, maybe as the PP poster said the mom got a job and is suddenly moving and everything is just going fast.

BUT, maybe they met online and the guy has never met his "step child" and the child does not cope well with all this change. Now a days, who knows! The child is 3.5 so is at least older and can vocalize their thoughts and feelings an needs etc. But if they are moving and leaving old car and starting new car all in a matter of days the child may not adjust to well. I'd have to meet the mom, step dad and child and I'd have to get a really, really good vibe from them and they'd have to answer all questions perfectly for me to take this leap!

As I said, make sure you have an easy out and make sure they pay for care in advance so you don't get burned. In cash...a cheque will take 5 days to clear and you won't have the cheque until the day before care starts.