My goal is to purchase 15 units in the next 5 years, and produce a cash flow of $20k per month within the next 10 years.  

I think if you just attend any group, you'll find investors that purchase remote and local and you'll be able to learn.

If you do have to move because of a job, you would be safest (in my opinion, i am not giving legal advice or financial advice), i would sell that property to ensure that you did not just purchase with the goal of moving out early and taking advantage of lower rates and lower down payments for purchasing your home as a primary residence. 

Or buy something that needs some love and some hard money lenders will fund up to 90-100% of the purchase and rehab.

That someone is going to deliver to you, on a silver platter, a property purchase you can simply say "yeah, sure, I'll take that" where you do some paint, carpet, little cleaning and tidying and turn around and clear a $100k? 

I’ve joined some of these before & they often feel like sales pitches or marketing ploys, but I won’t be pumping people for information or trying to make a mailing list or any of that.

The substitute of collateral was more of a scenario where you sold for $155K, and instead of paying off the $88K loan in your scenario, those funds stayed at the title company and were used on a cash purchase happening nearby in date. 

Someone who can't save up for a new purchase every year but still has a lot of desire for growth in their area of expertise.

In Berlin, rental arbitrage has been very profitable, with average annual margins of 25-40% after all costs but before taxes, so shifting to a market where arbitrage is barely breaking even is definitely a reality check.Given your experience, would you say the best way to enter the market now is through purchasing properties with financing?

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