There are plenty of people at retirement age who do not have $500,000 liquid (or illiquid) on their personal balance sheet.But that 28 number has a downside ... you have a long way to go in your life and lots of things can happen in your personal life and in your real estate business that will alter your business and goals.First, to earn $10,000 per month ($120,000 per year) on $500 K is a 24% return ..... possible BUT you probably can't count on that much return EVERY year in any investment (OK ... somebody will dispute that assertion).I suggest that your (soft) goal for the next several years would be to double your capital to $1 million by doing what has worked for you.  

Is it the case that MOST mortgage lenders require 2 years landlord experience to count rental income, and only a FEW of us like @Dan P's lender and my firm will do the silly online course and consider the box to be checked? 

Keep in mind that the extra debt of the secured loan will be counted against you, when qualifying for the mortgage. 

Refi usually means that you get a portion or whole of your principal back, so in this example, you may want to count that $85K as return of principal, not ROI.So, your initial position is $100K cash.

Do I have to put all my cash in or does it count to have part of it as a mortgage?

Based on income both from employment and passive income, my debt to income ratio after financing is will within tolerable guidelines after financing for the quad without counting rental income from the three units I will be under 28% for my back end ratio.    

As long as the entity pulling your credit is pulling a tri-merge report (all 3 bureaus) for mortgage services, you can pull as many as you like in a 30 day period and they count as 1.

The other income you have would need to show up on tax returns and would need to be averaged for 24 months to be counted. 

I’m thinking making sure someone isn’t now a registered sex offender or arrested for domestic violence would count.

I might be in a rush and forgot to count the cash so they didn't pay the full amount so it's now a you say I say situation.3.