Do you guys have investment accounts?
When I did the I-864 about a year ago, I could not use my wife's income since it was a contact position and there was no guarantee that it would last after she got her GC. I was short on the income requirement, so I included my investment account and provided a copy of the latest statement. I also had a family member that volunteered to be a co-sponsor. When we went to our interview, I inquired about the I-864 and the officer said that is handled at MSC and it wouldn't of gotten sent to the DO if it wasn't approved. They accepted my I-864 with the investment account in full and didn't even look at the co-sponsor information.