Additionally, keep in mind if you do this in a Roth then there are NO taxes on the appreciation, rental income or profits when the Roth liquidates the asset. 

Getting a base 8-15% return instead of 2-3% before actual “profit” puts you way ahead of the cash buyer. 

After months of reassemble and some customization work, the property sold for a decent profit.

Those things won't matter if your business crushes it. i feel like it would matter when those things add up and start tearing at ur profit If banking fees cut into your profit, your profit isn't big enough.

Back before I retired, I didn't need any of the cash flow at all so all profit just rolled back into more properties.

Keep in mind the more you write off the less money you will show as you net.If you have (2) full years and depending on how the accountant files your taxes you will have a schedule C more than likely or another schedule that shows profit and loss.

Also, when you say you cleared $550k in revenue, where did that put you for your net profit?

How about the simple obvious that the inputs to deliver the service/product have a base-line and market prices have, OBVIOUSLY, been at about as lean of operating profit margins as can be. 

Caveat is that you should be reinvesting those profits back into other smart investments so that you aren't missing out on compounding gains. 

The fix/flip might be a good way to get such a relationship started: usually has lower cash out of pocket requirements and you can sell the property faster to recoup the capital invested, plus any profits.