Still with one foot into listening to Dave Ramsey, I did a 20 year mortgage instead of a 30, which initially reduced my potential cashflow.

That form/framework isn't really there for investors, it's there for new construction when the initial appraisal is done before the framing is even done.

I'm pulling about a quarter mil out of some SFRs and trying to decide on buying a block of SFRs in Birmingham or stepping up to a small multi in Northern Jersey.

To be able to not only defer the cap gains from your initial investment, but as well as your new investment is amazing. 

You should incorporate those into your initial fixup cost. make notes of remaining life of big ticket items (e.g. roofs) and see how much money you have to save every month to cover those capex (which you can save from your rents).

Even if they don't know anything about rehab costs, and can't even find you the property, you would at least have the ARV part of the puzzle figure out, which is step 1.

Basically what I’m saying is just aim for one deal and focus on that first stepping one foot in front of the other.

After the initial camera inspection, the plumber located the breakage due to roots. 

Initially I dove into bigger pockets, talked with friends/family, identified my partner(s) and started reading a LOT.

I would like to buy a multiplex and I’m a first time buyer. I want to start investing and building a portfolio... where do I start and what is the best process to learn?