When building a deck or exterior stairs i would lean towards redwood or a synthetic product such as Trex depending on the application.

Wood floors but looks like it needs new kitchen, windows, bath, and some exterior work.

I've seen lots of semis with two exterior colors, two shingle colors, a half-new driveway, etc.I think the only way that you could split any other configuration of a duplex is by making it a condo and collecting HOA and having a condo corp... which for two units is absolutely ridiculous.

Here's the first one which definitely needs some cosmetic work on the exterior https://www.redfin.com/VA/Hampton/9-E-Cummings-Ave-23663/home/52046211And the secondhttp://www.realtor.com/realestateandhomes-detail/1203-Victoria-Blvd_Hampton_VA_23661_M54776-86930

The governing documents should have strict guidelines that cover all aspects of the association from the Board's rights and powers, to a code of conduct of residents and renters to a process for making exterior modification to individual units.

You want to make improvements the increase the market value as compared to properties in your area.How does the exterior look?  

Just based on J Scott's numbers I am overpaying for interior paint but underpaying for exterior stuff. 

Assume $5k per unit counting the exterior as a unit.

Exterior and presentation is key.

I'm doing a full rehab of the property: paint, kitchen, flooring, exterior, etc.