However, we found receipt management (downloading emails and pictures and saving them to Google Drive) to be so cumbersome and decided to join QBO train.

Last I checked my average across 30 units was something like $179/door.

If you want cashflow.. look for markets with low entry prices and higher rent averages.

Average of 40 days on market.

If this is how a cash out refinance works, it feels like the strategy is to either have more to rent out within the property (multi-family), wait for average rents in market to increase, rehab the property more and increase rent more, pay off the property/ more of the mortgage and refinance again without a cash out to decrease the mortgage (I don't even know if I can refinance a property twice)? 

Then, obtain quotes from at least three actual contractors. ( insurance and all that depending on the work)You'll likely encounter three types of contractors:The Super Expensive Guy: Highly skilled but often in high demand, resulting in premium pricing.The Average Guy: Offers good quality work at a reasonable price.

Once you get out and find your local REIA or meetup, you will build confidence on top of the information downloads because people just like you will already be doing what you want to do.

The average sale price for Condos in the NYC Metro area is $649,000 in the last 6 months. 

One option is to give the front house a credit for water based on averages, but I don't know if I would agree to that as a tenant. 

I have a nearly couple dozen in the area and my average rent is almost $900.Be careful who you take advice from