I know a lot of people concentrate on older homes but........don't forget a lot of the criminal/tax evaders/suspicious element of today still live on cash and don't use banks
I know of a stripper who had 16 grand stashed in her home......which was suposedly stolen by her ex bf. I also know of an ex outlaw who died when I was younger. He told a friend of mine he buried a box of money and guns in his back yard but couldn't find it because he went blind rather quickly. He died shortly after. I'm thinking of asking the current owners if I can detect the yard. It's been 25 years but hey....you never know, he may not have retreived it.
Gangsters........pimps.......bookies......loan sharks.....married men
all have money stashed somewhere. If you buy a home, it's always worth a look around.