I am afraid that most of us can't really give you any viable suggestions. You guys have to weigh together the benefits of having one child, versus having two, and figure out the challenges, and whether they are surmountable. I think that being older, (than in your 20's) you are much more realistic about the down-sides, whereas you might have simply rushed forward in your 20's without thinking. It makes some decisions wiser ones, and others just plain "tougher".
So I think what you'll get on this site is lots of stories about other people's lives, rather than really viable advice for your own. But maybe there will be a message in there anyway . . . .
I have 4 girls. The first two were born before I hit 30, after which I was divorced, played single mom for 5 years, then married again at 35. I kept asking my husband if he wanted a child of his own, cuz my clock was ticking . . . and he said he was happy with the two we had. Then I ended up getting pregnant and having a miscarriage. (which was a good thing, actually, cuz I had been 100% sure the pregnancy was screwed up to begin with -- I just knew something wasn't "right" in there) Then when I was 39, I gave birth to our 15 yr old, and at 40, I gave birth to our 13 yr old. They are all of 20 months apart, and were both unplanned. Now I'm 54, and sometimes I do look around at my friends with empty nests -- once in a while I think of the things we could be doing if our "younger" two were grown up -- but you know what ? 98% of the time I think, "Oh my gosh ! What we'd be missing if we didn't have the joy of these two girls in our lives.
They have kept us feeling "younger" because we hang with people who have children their ages, rather than empty nested adults. Having my youngest at 40 wasn't really a problem. I think that's probably based on individual health, and I've always felt younger than I am age-wise. Being in my 50's, I don't think I'm as "exciting" a parent as I was to my older girls, but on the other hand, the younger two have parents who have more perspective on life and are more able to put their own needs down in favor of doing things that are important to them. We aren't trying to live our lives through them, or have "perfect children". We are enjoying seeing the people they are becoming, watching them complement each other, watching them argue, even. We just thoroughly enjoy them.
that is us, though, and you are you. If you want to have another child, and your husband wants to continue his education, why don't you check out those options ? I suspect neither of you are "day care" fans, since he opted to stay home with your daughter, but there might be a day care facility at the university, staffed partly by students studying early childhood education. And he might be able to take a few classes, with the kids in daycare, then bring them home while he studies. Check out the financial aid options. I think the best thing you can give your children is parents who are fulfilled, challenged and happy with their own lives. It's a great nurturing ground for them to model the kinds of attitudes and behaviors that get you there.
Take care. It's a big decision. . . I'm kind of think you're asking because you're leaning toward having a second child, otherwise, why even think about it ? . . . but it's your decision and your husband's decision. Or, with us, it was just bad use of birth control both times ! (But we were delighted !! We just didn't do any real planning to get there. We like surprises.)
Good luck, and blessings -- with one child, or with two children. Being a team of a family is a wonderful way to walk through life. :-)
barb