No matter what your household registration is, you don't have to buy rural basic medical insurance when the unit pays social security for you. Neither can be saved.

If you pay the rural basic medical insurance first, and the company wants to sign a labor contract with you and pay social security, you need to cancel the rural basic medical insurance account first. When you go to CCB with your ID card and the company's letter of introduction, the staff will tell you a phone call to help you cancel your original account, so that you can apply for a social security card, and then the company can successfully pay social security for you.