A secure home is never "absolute" but there are some things that can be done to make them more resistant to break-in. While I make no attempt to verify the relative security of a home, one simple thing that I do like to check is if the security pin on the lock-set enters the strike plate on the door jamb. Some lock-sets don't have a security pin as part of the mechanism and some doors (like doors with interlocking type weather-stripping) are less vulnerable to tampering. The typical steel or vinyl insulated type doors with compressible type weather-stripping can almost always be opened with a credit card if the security pin enters the hole in the strike-plate (in-swing type doors) or with a knife from the outside (out-swing type doors). The strike plate can be adjusted to prevent this and repairs should be professionally made. In the picture below, the security pin is the little bump on the right side of the strike-bolt in the edge of the door. 
Out-swing type doors should also have what is called "security-pin" type hinges. These hinges have a small set screw that prevents the pin from being removed from the hinges on the outside when the door is locked/closed. It is also a good idea for these out-swing doors to have security plates over the latch mechanism to prevent access to the strike bolt from the outside.
If the door has a dead-bolt or other secondary means of locking the door the security pin issue is also reduced----but you have to remember to use the dead-bolt.
So check your doors and see what you find.
Charles Buell
www.buellinspections.com
Charles Buell, Seattle, WA, Home Inspector
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Interesting observations, Charles - and a good example of the service you provide to your clients. Do you recommend that owners replace these security-pin locks with dead-bolts?