I don't think your math makes sense.

For anything less than that with a traditional bank or credit union, you'd likely be looking at a portfolio product (the bank/CU will hold your loan and not sell it on the secondary market). 

Perhaps he runs negative cash flow while repaying the purchase loan or there is something I missed so my math didn't add up properly.  

We're not curing cancer; it's just buying real estate, doing some basic math, buying some furniture and kitchen utensils, maybe getting creative with some amenities, and listing properties on STR platforms...it's daunting when you're new, certainly a grind to get started, but it's not a mystery or puzzle to solve.

It seems like it basically up to you to do the math on how much more you will potentially make selling each unit individually and then deciding if that extra $$$ is worth the number of extra hours you will spend.

Paper napkin math says skinny deal. 

If I did my math correctly, on a 3,600 SF triplex where you buy the land for $150k, you generate a gross profit of about $84k (based on a $140/sf build cost and sale price of $205/sf), before you pay interest on any borrowed funds or closing/commission costs.

When we did it, we did score some great deals, but what we found was that we were visiting so many properties to understand our "strike price" (the maximimum we would pay for the property when taking into account rehab costs, hold times, interest on any debt, closing costs, real estate commissions, a contingency reserve for "unexpecteds", etc) that the math started to not make as much sense.

I am a high school math teacher from the Pittsburgh, Pennsylvania area.

Quote from @Nicholas Dillon: Basic math on a napkin.When you cash out the equity, you borrow it from the bank.