If you want to look up someone, never go to so-called police friends; they can look it up for you, but it's illegal. Remember these four websites, which you can check easily from home.

The first, China Judgment Documents Online. Enter their name, and you'll immediately see if they've been sued before, if they've been convicted, or served time in prison.
The second, Enforcement Information Disclosure Website. Check if they're a defaulter or if they've been enforced by the court.
The third, Enterprise Credit Information Publicity System. See how many companies they own and whether they are shell companies.
The fourth, People's Bank Credit Reference Center. This is actually the most important; a credit check will reveal if they owe money or have loans.
All of these are public and legal channels. Asking for help is not illegal, as long as you can check everything clearly.