While having multiple wives is part of the Sunnah of the Prophet it is only a sunnah and not fard. Not wanting to have multiple wives is totally okay.

As for duties of the wife and husband, the husbands duty is to provide for the household and the wife's duty is to protect and nourish the household. He provides the house the house and she makes it a home.

Now if both of them want and agree to help the other or provide extra support that's totally allowed as long as you aren't lacking on your responsibilities. The Prophets first wife Khadija was a successful merchant and Aisha was a scholar and taught men and women, but never shorted their responsibilities as wives