The deed to your house is recorded at your local municipal administrative office, and is public record available to all. Once you buy the property, your name goes on the deed, which, again, is public record. As soon as your name goes on there, anyone, including private companies whose sole purpose is to solicit you for business, has access to it AND has your home address (literally on the deed). Your phone number is also, generally speaking, in the public record, and once they have those two things, they’re off to the races.