Usually I offer the mom two choices - one is to pay half my regular fee to hold or to take their chances and confirm two months ahead. The problem with holding is what if next week you got a call from a parent wanting a space in the next month. Are you really going to say sorry I am saving for next to nil income for 6 months and hoping the mom doesn't change her mind in that time. Whatever you do make sure the contract says non refundable. Then if she changes her mind you get to keep what has been paid. If you change your mind you have to give it back though.

I probably would tell the mom to contact me again in January and at that time set up when she wanted to start the child and ask for a fee from Jan till then.