Most part time and full time investors use these loans due to the simplicity and straight forward qualifications. 

Also lots of sellers have locked in <4% rates and don't want to buy at 7% new investors who dont have low rates will just deal with the new normal or historic rates.

There're quite a few more opportunities/strategies to consider, especially for high-net-worth and/or high-earnings investors.

Here are a few alternatives to consider for your next property:One option is debt-service coverage ratio (DSCR) loans, which are specifically geared towards real estate investors.

I tend to believe that could be a reasonable stat for the experienced investors, however, I don't know where you even get enough accurate data to formulate anything.

You'll have far less competition as you move into the 5+ unit space where the different financing and higher prices weed out many of the first time investors feeding on $400k fourplexes. 

If you pay more, you won't meet your metrics and will probably have negative cashflow and/or equity.You may have to make 10, 20 or even 100 offers to get one accepted at the price that meets your numbers.This is what all investors did BEFORE the Great Real Estate Crash of 2008-2010.

I've been down this road with a couple of investor clients before.

It was a significant milestone and ignited a newfound confidence in my abilities as an investor.

We're all investors!