Do you find that expenses are usually 50-60 of income?

You will find quotes all over the map which are usually apples and oranges as CPAs specialize in different things and have different business models (Flat fee, Subscription, Hourly, Hybrid etc).

And you could always charge a little more because of it but I feel like landlords usually pay water around here.

The grates are usually too dirty for me to fool with grilling when I'm there! 

I usually don't chase bad money with good and agree that your $20k against a 6 figure monthly bleed won't move the needle.

Usually income will have to work at the fully amortized (principal + interest) rate. - Lower down payment programs. 

Takes rent money directly out of their account which is usually deposited by the 5th of the month directly into my account.

Usually, when people are in a market such as Boston, that scaling is easier is DSCR loans because there is not DTI.

A mixed way is often best, with plans for money coming in and extra backup for any surprises.

Best use of this "extra" money has seemed to be for paying down payment of 3 additional homes per year at the 70-90k price range. (15-20k deposit each, 5-15k repairs each, additional cashflow avg 320/mth each).