Yes, you should change the locks as soon as you can after completing the purchase of a house. This is a matter of privacy and security, as you have no idea how many copies of the keys the previous owner made. You can change the locks yourself or hire a pro to replace or rekey the lock, which costs $50 to $100.

Smart locks offer a similar level of safety to traditional or conventional locks because they often use comparable locking mechanisms, such as deadbolts. The primary difference is the access method: smart locks use a login or code instead of a physical key, which adds convenience. While not inherently safer, some smart locks have added security features that can deter intruders, like shutting down after too many incorrect code attempts or being harder to pick. For the best security, it's recommended to combine any lock with other home safety features like motion-activated lighting, security cameras, and window and door sensors.

It’s possible, but depends on the design of your lock. Some door locks that lack a keyhole do boast a small hole on the exterior handle or knob. This hole’s primary function is to allow water to drain out of the lock, in addition to giving homeowners an easy spot to insert lubrication. However, you can typically use a paperclip in this pinhole to unlock the door by manipulating the mechanism inside. 

Security experts recommend deadbolt locks as the most secure option for a house's exterior or entry doors. Deadbolts provide the best security because they can prevent most types of forced entry and are harder to lockpick. Common types include the standard single-cylinder deadbolt, which is often found on front doors. For enhanced security, you can opt for a double-cylinder deadbolt, which requires a key to operate from both the inside and the outside.