You’re buying a house with security components
A new house may come with a home security system. All the components work, are installed in the right spaces, and are ready to go. In this instance, just pick up the phone to call and establish a new contract. A Vivint expert will still come to your home to make sure there are no integration issues, and they could offer suggestions on upgrades. It's a fast visit, and you can get your monitoring set up without paying for any new alarms and cameras -- unless you get some new devices.
The outgoing homeowners can give an existing Vivint contract to you for a nominal transfer fee to make the transfer a snap. If the owners are downsizing to an apartment or retirement community, turning over the home security service might be a condition of the sale.
You need to move and take your old equipment with you
You might want to take your existing smart devices with you to your new home when you move. It should be pretty easy to do, as most alarms and smart devices are portable. You can remove each device yourself or contact a professional installer to come and take down the system. Then a pro will put in the same devices -- and any smart services you need to add -- in your new place. Your home security contract will remain the same.