Sounds like a cash out refinance would be the best way to tap into that equity. 

I've read numerous guides and watched many YouTube videos, so I have a good theoretical understanding, but I'm still unsure about the best way to start investing in U.S. real estate.My plan is to begin with long-term rental properties and then eventually move into flipping and the BRRR (Buy, Rehab, Rent, Refinance, Repeat) strategy.

I figured this could possibly put me in a good position for a cash-out refinance when I’m ready to move on to a second property.If I stick within my budget, Philadelphia seems to offer the most housing availability, but I’m concerned about most houses available being in rougher neighborhoods.

Something to consider maybe using one of these companies to help find a house, refine your process by example of what they are doing, then taking over management for a year and seeing how it goes.

:)  Is it still cash flowing after the refinance?  

You have used home equity lines of credit to purchase investment rentals and want to know the best way to pay down the HELOCs.Between the two properties you bought, after expenses, you have $250 a month positive cashflow to use.What I like to do is pay down some principal every month with my positive cashflow.I use my extra active income from real estate commissions helping other investors to pay down the principal even more which just frees up that credit for me to use again.I know I can refinance the HELOC debt before it changes to principal and interest as it is just interest only payments as yours are.One difference is the cashflow, I have greater positive cashflow and could make the principal and interest payment in the future with the extra cashflow I already enjoy.I always get HELOCs on my income properties as well after purchasing them to pull out as much of my downpayment as possible.

And if you bought this property several years ago, then you probably already have a killer rate, so suggestions to refinance seem silly as you probably already have the lowest rate....especially if your refinance was completed as you were an owner occupant, and not categorized as an investor to a Lender.In terms of tax implications, again, it depends on what your ultimate goal is, but if you placed this into a trust, or even a beneficiary deed, it would pass through to a beneficiary who would not have to pay capital gains on it in order to sell it. 

Refinance with Rate Buy-Down:Pay 2 points ($8,640) to lower the mortgage rate to 6.625%.

Wait till rates are back in the 5s, refinancing/HELOCs are expensive today and you will need to refinance that debt in 1-2 years anyway once rates come down.

Focusing on the best quality real estate will allow you secure more favorable financing terms, more likely to achieve favorable exits/refinances, more likely to attract the best capital partners.