Assalaamu alaikum Friend Anonymous,
(smile) Each person, and each couple is different. (smile) No one can answer this question for you, because we not only don't know anything about you, but this is something you have to decide for yourself. If your potential spouse wants to wait, you'll have to decide if you want to do this or not. (smile) Sure, look at fertility potential, economic or social factors, and your personal factors and dynamics... but at the end of the day, you have to choose the situation you feel is best for you and your future family.
(smile) So I'd recommend you think carefully about what you would like to do. Ask advice of people who know you better. Try to get to know your future spouse. Do research on specific points that are important to you and your potential spouse (like fertility potential with age, for instance. Or child-care supports, if needed for a spouse to finish studies, for example). (smile) Walk in the winter woods/ summer plains/ by the seashore... and think and open your heart to His Will. Then pray the istikharah prayer, and make a decision.
(smile) And then leave what children may or may not come in Allah's Hands.
May God, the Bestower, Gift us with what is best for us... and may He Help us to be grateful and satisfied with His Gifts.