Very important question that is often overlooked. I think empathy and emotional support are critical factors. Entrepreneurship especially the startup years, can sometimes feel very lonely. During this time u want to have a partner who understands you even without a detailed explanation.
Also critical is someone who can ask tough questions but will stay the course with you especially during tough financial decisions such as taking out money from a retirement account or a home equity to pay for employee salaries, etc.
My research into high growth Indian American immigrant entrepreneurs showed clear evidence that spousal support was a key factors that helped them stay the course during tough economic conditions.
Let me know if I be of further help!
BTW let us know how it goes :)
Good Luck!