In the C/O Refi scenario, I'm using a 70% LTV ratio against the value of the properties, then subtracting the liens and the borrowing costs to get an estimate of what I could extract.

In our case, it just felt like another tax to extract monies for the city coffers.You may want to call your city anonymously and just ask what the process is if you bought a house and prior work was not permitted.

These variations in assumptions surprisingly have a meaningful impact on your returns / interest payments over the course of the loan.

I intend to store money in a savings account from rent and from wholesaling.I have also heard from a few people that they were able to get a meaningful chunk of cash ($3,500) when they opened an account to start their house flipping business.

Nasty messages painted on walls after eviction, yup, but it really is so much more meaningful when done in poo I just never understand why it's always hand applied.....

(Extract lists, cold calling, etc.) 

With single family properties, the property is either 100% occupied or 100% vacant so a meaningful vacancy rate is harder to determine.

And unlike many of the cash flow-centric markets @Ali Boone listed, you have the potential for meaningful appreciation if the positive trends in many of these intown neighborhoods continue. 

Its easier to extract $100 from $1500 in rent than it is from $300.

This could help you find areas where there will be a greater likelihood of meaningful appreciation as opposed to just the cash-flow game from depressed purchase prices (a lot of Ogden).