You’re moving into a place with home security devices
A new home may come with an installed home security system. All the alarms and cameras function well, are installed in the best spaces, and are ready to go. In this instance, just get the phone to call and establish a new contract. A Vivint installer will still show up to ensure there are no usability problems, and they might offer options on upgrades. It's a preliminary visit, and you can get your monitoring set up without worrying about any new devices -- unless you get some new devices.
The outgoing owners can move an existing Vivint contract to your family for a nominal transfer fee to make the process simpler. If the previous owners are downsizing to an apartment complex or retirement community, you keeping the home security contract may be a condition of the sale.
You want to move and take your old components with you
You may need to take your favorite home security components with you to a new place when you move. Luckily, it's fairly simple to accomplish, as most smart devices are plug and play. You can take down each alarm or camera yourself or call a Vivint expert to dismantle everything. Then a pro will hang the same components -- and any smart devices you need to add -- in the new place. And your home security contract will stay the same.