DH and I are also thinking of keeping any board she pays and giving it back to her when she moves out.
A friend of mines parents did this and it was given to them upon the purchase of their first house. I think it is a great idea if you can afford to do so.

We started by putting away $1 a day for each child when they were born, it is managable and with interest it might help them out a little. We also put any money they receive for birthdays etc into their accounts as they get more than enough gifts and are to young to understand. We also have a money box that any spare change is put into, this is then divided into the girls accounts, it all adds up but without putting any strain on our finances.