The longer term loans would have lowered your monthly payments and decreased the costs.As for rent, each year you need to look at rents in the area to decide how much you will be increasing the rent by. 

White Oak color and Walnut color are the two main ones you want to focus on, depending on the rest of the design in the house!

Without actually building the 3rd unit, would this new triplex eligibility increase my property's value? 

The importance of lowering expenses and increasing efficiency to maximize property income.

That will show what proposed tax increase you will see.

Sounds like an easily executable deal from what you've stated but likely need more color to offer path forward, terms, etc.

Colors, quality of paint, how much prep needed, holes patches etc. 

I did a recent flip with much warmer colors, actually used SW Creamy on the walls, and the house sold in 5 days. 

For one, we use the same colors on all properties so it would have to be painted that color.

What Brand and color paint would you guys suggest?