You can do a lot of the projections you're talking about in financial planning software, like estimating RMDs. 

The goal with this strategy is to have low living expenses as your tenants are helping you pay down your mortgage.

We are embarking on a construction project to build a 6 units onto a piece of land(30 yr fixed loan).  

What are your goals?

Columbus may offer lower purchase prices, but as you mentioned, oversaturation from investors could affect rental rates and appreciation in the long term.Considering your interest in Philadelphia's vibe and your desire for a potentially better investment environment, it seems like Philadelphia aligns well with your preferences and investment goals. 

What matters most is whether the numbers make sense for you and your investment goals.

I do think the rental market is ok, but I have found that a lot of NJ investors just look out as far as the prices drop.There are a lot of cool towns with better rental opportunities likely a little closer to you, but it depends what you can spend and what your goal is.

Within a few thousand for a generic rental rehab and again as a generic flip rehab is probably fine.My advice here is to use your network: find folks who are doing a lot of renovations for flips and/or rentals and ask them if they'd share some numbers for you for recent projects.

We can only hope for better standards in the industry.The goal of such types of legislation isnt to set the bar higher.

IF that is your goal.