Do you think that demand will be high for something like that? 

However, the high down payment and reliance on a DSCR loan could limit flexibility, especially with your DTI constraints.

I added a bedroom to my two bedroom suite due to high demand last year. 

Find one that can be custom to your needs, has flexible pricing, no long-term, high-cost memberships and excellent customer services to determine how to best market to your leads.

Because I live in a neighborhood that has no crime but it shows up as very high crime because we had two neighbors who would call the cops over each others dogs barking so it lit it up to show it as negative…

HOA fee's do not just shoot up that high unless there is trouble from a legal standpoint.

Knowing the three cities mentioned is important for grading the neighborhoods and can vary street by street. 

Unlike a kitchen or bathroom renovation your literally building a second house on the property and your dealing with everything from grading, soils, foundation, electrical, plumbing, framing etc.

One thing I think I would do is either hire a professional market research company and/or get a local high school or college marketing class to do market research and surveys to see if there is interest and demand. 

I have a some of high interest debt I used to start my business along with some personal debt I would like to pay off.