I asked my husband your question and he said "having a child is demanding proposition. It takes a lot of resources." He says for men a lot of practical issues come up, the demands on time and resources, having time for both the wife and the child, job security, the drag on the marriage.
For women it is a much more emotional and hormonal issue, having a lot less to do with the practical side of things. For instance, my husband was not ready to start trying until we were more financially secure and living in a better place and had a higher standard of living. (broke and living in a distressed trailer house is no time to have a baby. )
My husband said a lot has to do with current circumstances too. As far as having a second child, or when to have a second one. "Did he sleep on the couch for nine months? Do they still have a toddler in sleeping in their bed with them?" We had a really rough time with our son and my hubby did sleep on the couch for almost an entire year while I co-slept with our son. We now all sleep in a family bed, which my husband does not like, but works best for me and our son right now. Did you have a rough time at first with your daughter? could that be reason your husband is hesitating about a second?
I noticed your husband is going to school and you work part time? Is he worried about your finances? This is always a biggie for my husband. Especially now with the unemployment rate so high and job security not so secure anymore.
My short answer is that you can't "convince" him to "be ready". And if he is anything like my husband, putting any pressure on him with make him back even further away from the idea. I waited more than a few years to start trying for our son, and I have been wanting a second for about a year now, but we have just begun to open a dialog about it very recently.
Not that your husband would abandon you and your child, but I believe it is better to have both parents fully on board when it comes to a planned pregnancy. It was hard waiting for my husband come around to being ready to start for our son, and it is hard now waiting and not knowing if he will ever be ready for a second child, but I definitely feel it is worth waiting for him to for him to be ready on his own without pressure from his wife.
The best advice I can give you for getting him in a more ready frame of mind without pushing him is to try to get together with other couples who have two young children so he can see what it is like for others.
I hope this has been helpful Feel free to send me a private message if you would like to talk more about this.
Jen