In all seriousness you should not marry until you have your career figured out and know where you're going to live should children come around. Probably you should know that by the first couple of years after your mission but it may be longer for others depending on their circumstances. What I'm getting that is not everyone can be placed in the same boat. I think you can manage as a couple and still study and work but by the time the first child comes everything changes!
I'm a Roman Catholic here in Spain and I don't think there is a specific age for people to get married but I do understand the concern some mormons have. As long as they're happy and they know what they're doing and they have jobs, etc I think they can successfully make it. My parents worked very hard in order to provide for me and my siblings and we weren't rich.