Refinance commercial multifamily home from residential loan

[Jakobe Smiff]

I recently purchased a 4-plex at $640K, with financing though a residential loan. It was appraised at $647.5K based on the gross monthly rent of $3500 multiplied by the Gross Rental Multiplier of 185. We recently added a 5th unit, renovated the house, and had it zoned with the city as a commercial 5-plex. After the renovations and adding the 5th unit, we are getting monthly rents of $5,600. If I use the same Gross Rent Multiplier of 185, that puts the value of the home now at $1,036K. 

1. Is my math right on this? Will a commercial appraisal follow this same formula for the value?

2. How do I go about refinancing the home on a commercial loan so that we can pull out some of this new equity and continue the BRRRR method?

Thanks!