Seasoning for 2-Unit Rental Formerly Used as Residence?

[Will Johnston]

Last year my wife and I started renting out the house that had been our primary residence.  We wanted to purchase another investment property, but our lender informed us that we could not use the income for six months.  This, of course, made our debt-to-income ratio all out of whack and we were unable to purchase the additional property.

Currently we are considering buying a two unit property and living in one of the units for a year. After that, we'd look to purchase another SFR to live in longer term.

I'm wondering whether we'd be able to use the rental income from the two unit property to help qualify for the new mortgage immediately or if we'd have to wait the six months.  I'm assuming we'd have to wait, but I wasn't sure if there was a different rule for multi-unit properties.

If we can use the income, would we only be able to use the income from the unit we had been renting out longer term?  Or would we be able to use the income from both units?

Thanks in advance!