You’re moving into a place with security components
A new home may come with a home security system. All the devices work, are hung in the right places, and are ready to go. In this instance, just get the phone to call and set up a new service contract. A Vivint installer will still come to your home to make sure there are no compatibility issues, and they might offer options on where you should replace bad outdated components. It's a preliminary visit, and you can have your 24/7 monitoring set up without paying for any new alarms and cameras -- unless you get some new devices.
The previous owners can move an existing Vivint contract to your family for a one-time set-up cost to make your life simpler. If the owners are downsizing to an apartment complex or retirement community, you keeping the Vivint contract may be a condition of the sale.
You are looking to move and bring your old devices with you
You might need to take your existing Vivint system with you to a new place when you move. Luckily, it's pretty simple to transfer, as many alarms and smart devices are plug and play. You can remove each component by yourself or contact a professional installer to come and take care of your devices. Then a pro will hang the same devices -- and any smart services you need to add -- in your new home. The home security contract will keep the same.