You’re moving into a home with security devices
A new house may come with an existing security system. All the components work, are installed in the best spaces, and are ready to go. In this instance, just get the phone to call and start a new monitoring contract. A Vivint installer will still come out to make sure there are no compatibility issues, and they might offer ideas on an upgrade or two. It's a quick trip, and you can get your alarm monitoring set up without paying for any new components -- unless you make additions.
The previous owners can transfer an existing Vivint contract to your family for a one-time transfer cost to make the process easier. If the outgoing residents are moving to an apartment or smaller home, turning over the home security service may be an addendum of the sale.
You are looking to move and take your old components with you
You may want to bring your existing Vivint system with you to your new place when you move. It should be fairly simple to transfer, as most smart devices are plug and play. You can uninstall each alarm or camera by yourself or use a Vivint expert to come and dismantle your devices. Then an expert will put in the same components -- and any smart services you want to add -- in the new home. The home security contract will stay the same.