Now the attorney says that the INS is having some doubt about the marriage, they need a lot more paperwork, has anyone had this problem and what did you have to produce besides the regular things, like rent, utilities, and paperwork that you both have your name on. Also they do pay taxes to the IRS. They have no children.
It occurs to me that the INS could be conducting routine and/or random checks on that type of marriage.
Your friend needs to rely on the lawyer to guide them through this.
As to what they'll have to produce it's likely to by anything and everything that will show that they have a real marriage.
I imagine that they might be interviewed separately a couple of times through the process.