"I can't wait to not have kids and spend all my money on myself."

This sounds strange because it is humor.  The expression is usually positive, but it can be negative.

I can't wait to not have to listen to the barking of the neighbors' damn dog!  The day they move is the day that I will have a big party and invite all my friends.

I can't wait to not have to listen to the lies of Political Party X on the news everyday.