I've always wanted to teach. But I'm scared now of dropping my career for four years to go back to school. I have financial obligations now. I wish I could study and work fulltime at the same time.... 
Just do a bit at a time ... if you can use something like the OU then they can help with funding if you don't have the income. You don't have to take on too much - just do a starter course first of all and before you know it you will be half way there and have the incentive to see it all through.