Example could you take data from census like housing starts and building permits, existing home sales, sales tax movements, housing market index, ect. and map it out like stock charts do, then use something similar to technical analysis as a predictor?

I'm glad I was careful to get permits for everything! 

I've had bids for the same job where the highest was 4X or more the cheapest.This usually requires permits and a licensed contractor, unless its a property you personally occupy.  

Here's the form: (see page 2, section 5)http://resources.baltimorecountymd.gov/Documents/Permits/rental_registration/rentalhousingapp.pdf

If I follow zoning guidelines when submitting permits is the process for getting approved to build pretty straight forward?

My company builds amazing affordable and green custom prefab modular homes that can be built for less then half the cost and half the time of a traditional buikt home with way less regulations and permit costs it's the future of affordable housing and we are here to answer and questions you have and I would love to show you more information on our affordable homes and past projects we have built.

That will involve getting a detail from an engineer, pulling a permit etc.

I would also plan 10-15% contingency into your home reno as your likely to run into some issues depending on your experience with home renovations and permits. 

It seems that duplex is permitted. 

The day after rent is due issue the pay or quit notice, apply late fees as permitted.