If the owner next door to you wants to add 2 more floors to his home and sent you a agreement granting license and indemnity should you sign it
I'm assuming that the neighbor needs access to perform the work. If that's the case, there is a proceeding that they can start in court where the judge will compel you to provide access. Negotiating an agreement with the neighbor where you are provided indemnity could provide a better outcome to a court ordered arrangement.