Ending a marriage can be a very painful process. If you feel you need time to see that relationship to an end before getting settled into something new, than I would trust your instinct. He should be able to respect this decision. However, maybe if you give a specific time frame he will be able to feel more secure about things, or maybe if you are willing to make other concessions. Personally, I wouldn't be able to properly focus on a new relationship if I were still tied to another person, financially or otherwise. But everyone heals at their own pace, so when you feel ready, try it, but if you don't feel ready, trust yourself.

Jumping from one relationship into another has it's own risks though. I would say be careful, make sure you aren't overwhelming yourself, and listen to your instincts. Perhaps talking to him about why it's so important to him will help you to make your decision, but also make sure he understands your hesitation and how you feel. Communication is key in any relationship, and it will be paramount to making things work with this one.