I used a combination of leveraging my business line of credit, HELOC and partnerships for my first couple deals before adding in private lenders. 

.$8kish / year or so on routine and reactive maintenance combined which should include your cleanings, lawn care, maintenance calls ect. 12% per month of gross rents should be a good estimate if you want to look at it like that!

The combined transactional costs alone between the purchase and sale are going to be north of 10% of the transaction value.

Also in your strategy lay out the combination of cash flow and or appreciation.  

This looks like a combination of interest rates and just relatively high prices still (e.g. most duplexes I've seen start at around 600k).

Owe 2 million with 5 million in value combined. 

I'm using a combination of MLS comps provided by realtor, redfin, and backflip analysis tool.  

We bought it for $225k with a 3.125% mortgage and 1) are interested in keeping it as our first rental. 2) We are thinking about using some of the equity (maybe $50k or less as a HELOC to combine with existing cash for our next home down payment that we can convert to a HELOAN through our credit union).

They started the business from scratch in 2003 with a combination of wholesaling, fix-and-flips, and non-conventional financing sources like private lending, seller financing, and lease options—which remains their expertise today.If you had one question for a professional real estate investor who retired themselves by 37, what would it be??

There is value in intangible assets, at least as much as it would cost/take to recreate it - and it saves the buyer the years it took.Like Don said, maybe not interesting for a pure real estate investor, but this is a combination of a business and real estate, you have to value both.