Valuation- Triplex: C buidling / C-D neighborhood

[Jason Reichert]

Newbie looking for some sale advice. 

Purchased a triplex as part of a 15-unit portfolio and am now entertaining offers to sell it separately. Having trouble coming to terms with my valuation of each building. I'm pretty sure the deal is great and the sale is fair; but I'm not trying to leave easy money on the table. How do I value a triplex in a C to D neighborhood? 

NOI and CAP are king?

Cashflow?

100x monthly income? 

Its all comps at 3 units?

Thanks in advance.