There's a lot of marriage mafia happening in india where female wouldn't divorce husband but live off his salary in their house which will be partitioned has the possibility of ownership as well. I know a family where the divorce ran for 30yrs, the lady seemed to wasted his life and career. She used to go to his office and scream at him and due to that embarassment he changes job often and he is not able to shift for work other city or country as well. He recently got divorce after 30 years now he is 55yrs.

So now a days guys tend to get some evidences by some spy tech filing divorce or clearing doubts.

Females are also scammed by guys after all analysis as well. People somehow tens to hide their loans and make their partners pay it off.

Regarding data, it can be got from anywhere. In the roadside store where people recharge mobiles, shopkeeper notes down names and number and address, that info can be bought. Nowadays easiest place in matrimony sites and from people who work there that's actually rich data where people describe about their family, status and groom or brides salary. Every year there data leakage from govt and private mobile companies with aadhaar details.

Hiring detectives are old school and works, some rich people do before marriage and social media analysis.