How are business partnerships "pre-qualified" for a loan?

[John Kaspar]

Hopefully this is in the right category. Anyway, a friend wants to partner up and go in on a multi together. That being said, we both intend to pull a HELOC on our homes and grab a multi. However, we want to start an LLC for a few reasons. Unfortunately I do not understand how they would go about approving us for an amount as we both would be just using personal funds. Where would the mortgage company come up with an amount? Would it be a combined DTI?