I totally understand where you're coming from on wanting to start the process now, we were in your same shoes a few months ago. However, based on what you've said, I do think it's too early. When you get pre-approved, the banks want to know about you last two years' earning history. My husband and I also recently graduated from grad school, and this made it a bit difficult to show two years worth of good income history. Since your husband is still in school and I assume does not have a job lined up yet, (?) the banks might frown on approving you for as much as you could get if you wait.
That being said, it sounds like you really just want to talk with a realtor about hidden costs in neighborhoods you're interested in. I think most realtors would be perfectly willing to give you this information before you're pre-approved and actually looking, especially if it means they might get to keep you once you really start looking!