If you are moving into a new home, change the locks right away. Although other tenants might not have a key anymore, they could have copied it. You can even buy and install the locks yourself so you know that you are the only one with a key.
Only provide your house cleaner with a key if you trust him or her implicitly. If you do give your housekeeper a key or plan on doing so, it is imperative that they are honest and upstanding. Carefully check their references. If you are using a cleaning firm, make sure it has an excellent Better Business Bureau rating.
Are you a female who lives on your own or with children? Are you not comfortable with the idea of physically defending your