Only you and your girlfriend can decided when the right time to start a family is right for you both. If you are not going to start a family until next year when your living together and are working and your schooling is complete then that gives you close to another year to make further decisions about this as its not something you want to jump into lightly and your relationship will be that much further developed. If you both desire a family then these feelings wont go away in this time just strengthen.
Best of luck to you both deciding when the right time.