You moved into a house with a pre-existing security system
Sometimes when you buy a house, a security system is already installed. All the components function well, are hung in the right places, and are ready to go. In this instance, you might see that you have to call and start a new service contract. A Vivint installer will still come out to make sure there are no compatibility issues, and they could offer suggestions on an upgrade or two. It's a fast trip, and you can have your alarm monitoring set up without having a bill for any new components -- unless you make additions.
The old homeowners can transfer an existing Vivint contract to you for a small set-up cost to make the process simpler. If the previous owners are downsizing to an apartment or retirement community, transferring the home security contract may be an addendum of the sale.
You need to move and bring your home security components with you
You might need to take your existing Vivint system with you to your new house when you move. It should be fairly easy to accomplish, as many alarms and smart devices are wireless. You can uninstall each device yourself or use a professional expert to take care of everything. Then an expert will put in the same devices -- and any additions you want to have -- in your new house. The home security contract will remain the same.