Crystal ball batteries are dead so I'm shooting in the dark. These are just shotgun suggestions.
1. Change all X10 wall switches to standard switches, or three way switches if applicable.
2. Check all the outlets for two tiny dials, indicating it is an X10 outlet. Switch out to standard outlets.
3. Any lights, fans, appliances plugged in to X10 modules, remove the modules and plug directly in to wall.
4. Check your breaker panel for an X10 repeater and or wire-in X10 filter. If installed correctly there will be two breakers, or one double wide breaker labeled X10. (ask previous owner if possible).
5. X10 also made "wire-in" modules. The wire-ins were used many times for ceiling fixtures. They are the same size as the plug-in modules so if you have any, they are likely mounted in the fixtures box (attic?). Again if possible ask previous owner.
This is sort of a 10,000 foot view. Could be more extensive, for example: did the previous owner leave any automation equipment or was home automation or phone control mentioned in the real estate ad?