That depends upon how you want us to make payments. Basically, we have to report income to the IRS for every person we send money to, whether it's an owner client or a vendor (unless they're a C-Corporation). So let's say your house is owned by yourself and your friend. But your friend is not interested in receiving any income from the property for some reason. Under those circumstances, we could send only money to you, and only report the income on your 1099, so we'd only need your SSN. Of course, the other owner would need to authorize this in writing, since they have a right to income from the property as an owner.
Now, if both of you want to receive income, we do have to have social security numbers for both of you, and we will have to report the income to the IRS for both of you. You'll both receive 1099s from us every January. Unfortunately, this is the law, so we have to comply with it.