How do you know that someone else does not have a key for your house? If you are not the first occupant then it is entirely possible that there are spare keys out there somewhere!
What if the owner of that key is a less than honest person, and chooses to use it to get into your house and steal your belongings? It has been known to happen, and is very distressing.
It may be that you have lost the keys to your house, and want to change the locks. You may be surprised to know that you can rekey a door lock using a simple kit from a hardware store.
Following these simple steps with a good rekeying kit can save a lot of money, especially if you have multiple doors! Begin with the door unlocked and the key in the lock:
If you do let the springs jump it is not a disaster your kit will include an instruction sheet that will tell you how to reinsert them.
If you are not sure about doing it yourself, contact an experienced locksmith who will quote you a sensible price for rekeying your locks.