What is the Proper Way to Value "Dual" Quads?

[Todd Magin]

I'm looking at two quads being sold together. Do I valuate them as one 8 unit property based on their cash flow (NOI / Cap Rate) or as two separate quads based on comps in the area?

Should I do both evaluations, and then choose the "best" one (in my favor) when making my offer?

FYI, the properties are taxed separately, so I can buy them using conventional financing.  The ability to get conventional financing along with below market rents (managed by a church) makes this deal especially appealing.  I'm early in the discovery process, but my (unconfirmed) numbers indicate that I'll get a 12% cash on cash return before raising rents to market value, and a potential 25% after rents are brought up.