Renting a house bought initially to live in

Hi,

We currently live in a town home that we bought as a house for us to live in. We have lived for over 5 years and are now looking for a change. We are not in a position to sell the house as it is underwater. We would like to consider the possibility of renting this house and moving to a rental property. My questions are -
1. Are we liable to inform the bank if we decide to rent it out? Is it legal?
2. Will there be a difference in our rate of interest if we decide to rent this property?

We reside in the state of MD. Responses will greatly be appreciated.

Thank you.