Know the laws in your state.  If you have a good lawyer, you normally leave a marriage with the assets you brought into it.  What you acquire as a married couple is split or negotiated in the divorce settlement.  It's wise to enter a marriage knowing the family law of the state where you reside.  Doesn't mean you have an eye for divorce and gain, just that you're informed.  No one likes to hear this until they go through a divorce, however.

You don't need your MIL's approval.  Make your own money and don't ask her mother for handouts.  If Mother wants to give you gifts, or give them to your wife, that's another matter.