Unless you are a corporation, I don't think (as a private person) you can legally check someone else's credit, even with written consent. You will probably have to pay a company to do it for you. There are plenty of companies that perform background and credit checks for a fee.
I don't even think (legally) an employer can give out info on an employee.
One thing to remember is this: Just because a person has "good" credit, doesn't mean they're going to be a "good" tenant and just because a person has "iffy" credit, doesn't mean they will be an "iffy" tenant.
If he was a homeowner, is now getting divorced, and told you he will be filing BK, why are you doing a credit check?? It's VERY likely both he and his ex ran up credit cards, etc and never paid them because of the pending divorce. This happens ALL the time ---- husband and wife looking to "get back" at one another and think that by ruining one another's credit, they're doing something. I've seen it a million times. Running this person's credit report isn't going to help you in any way, shape, or form if this is the case.
Your best bet is this: When he comes to sign the lease, make photocopies of his driver's license, Social Security card, and his last 4 paystubs. This way, if there comes a time you have to do any court action, you will have his information.