Plus, you would be competing with the avalanche of money from private equity buying up seemingly anything on the market cheaper than normal so they can turn them into rentals.

Multiply it by 2.5. 

I've experienced this myself using my own spreadsheets to calculate things like cash on cash, cap rate, gross rent multiplier, debt coverage ratio, and the like. 

(note which comment is top-voted, that sub is obviously full of realtors)Multiply that by a zillion realtors all over the country, all telling their clients NOT to work with you..That being said, not a lot of people are hiring loan officers right now.

Also, check the file place on BP for other eBooks.Regarding ROI, you may want to look at other metrics depending on the properties you're reviewing, like cash on cash return, capitalization rate, gross rent multiplier, and etcetera. 

Multiply that responsibility by several units and then suggest that you can’t remove tenant (at which point you’re likely to have more than 1 not paying) and even a good cash buffer, like most of us regularly keep, is going to be gone fast if we have to toe the line and the renters do not.

It used to be that you could determine your Effective Rate (ER) by multiplying your note rate (r) X (1 - your tax bracket), or ER = r (1 - t).

There are workarounds and ways to address all this, but when you multiply the number of properties with a number of issues and a short time frame to get it all worked out, it does get hairy.

Currently, I use a percent multiplier by rent: 5% for repairs/maintenance, 8% for vacancy, and 5% for capital expenditures.

You may be able to multiply that money if you do several flips with the money you get out of it.