If you or your tenant want to add a new customer to the rental agreement, click here to learn how to do this. If you refuse the application, send the tenant a written message indicating that the application is rejected. Be careful if you violate any confidentiality agreements between you and the applicant. If the application is accepted, invite the tenant and potential roommate to sign a new lease or a legal amendment to the current lease. If the tenant approaches you and asks for a roommate to be added to their lease, they should probably send you a formal written question. Normally, the tenant is asked to add a friend or family member to the lease. Remember that the people participating in the rental agreement are responsible for your property on several levels (rent, deposits, damages, incidental costs, etc.).