Depending on financing, it could cash flow anywhere from "meh" to "I can live with that". 

-A higher pitch roof has a higher cost and should be considered if your duplex will be infill into an area where there are other homes with the roof pitch, but failing that we have not found that it has a real impact on appraisal (we are in an area of lower pitched homes however so take this with a grain of salt depending on your market) and a lower pitch roof means lower maintenance and capex costs.

It will depend a bit on comps, similar to an appraisal. 

It's passive and the initial cost can be flexible depending on your budget.

Ultimately, the choice between vinyl plank flooring and wall paneling will depend on your personal preferences and the overall look you are trying to achieve.

It also depends on loans that you are trying to qualify for depending on credit, experience, and other factors.

Really depends on the route you are taking as to market I'd suggest.

Depending on whether you use a "light-doc" program or a "full-doc" program, rates will change.

Really depends on what you are looking to do / what markets.

For a 3 unit building with one unit as a commercial space/retail space I would use either a 7 or 10% vacancy factor and perhaps higher depending on the viability/business strength of the restaurant.