Cap rates for MF in small cities in Georgia

Hi, All

I am practicing analyzing MF deals in small cities in Georgia, such as Columbus, Macon, Griffin, etc.. These properties are mostly in B and C neighborhoods. What are reasonable cap rates I should plug in for a fast estimation on their values using Michael Blank's 10-min method? I am using 8% and found that estimated values for many on-market deals are only about 70% of what is being asked. Basically, I am using 10% of the current potential income as the vacancy rate and 55% of the rest as repairs and maintenance, i.e., NOI = current_potential_income * 90% * (100%-55%). Does this fast estimation have any value in serving as the first pass for analyzing small MF deals ( < 20 units)?
Thank you in advance!