Other criteria I look for in a SFH house hack: an easy way to split into multiple units, a walk out basement, an ADU, a garage I could convert, or lots of bedrooms. 

Assuming the mortgage servicer eventually gets the misplaced principal payment, you will have overpaid the principal of the mortgage when you make the supplemental monthly payments, and the mortgage servicer should return that extra principal to you, without question, when they ultimately close the books.The mortgage servicer will not return the interest portion of your payments, and in fact some additional interest may be due when this is settled, despite your ongoing payments, because the interest is collected in arrears.  

My primary question is, does anyone have experience converting a duplex into a fourplex?

I plan on getting my license within 30 days and eventually becoming a fix and flipper instead of wholesaling.

Eventually, I ended my relationship with the management company and rented the property out on my own.

Other criteria I look for in a SFH house hack: an easy way to split into multiple units, a walk out basement, an ADU, a garage I could convert, or lots of bedrooms. 

The initial idea would be to buy a single family, maybe a duplex, and start house hacking, saving a bit more, learning the ropes, and eventually if things work and prices go up, get it refinanced and buy another property with that money?.

We traveled the U.S. off of the cash flow property and eventually made our way to Portland, ME before selling in the 2021 market.

These are both great suggestions to eventually get the market rent in place while keeping current tenants happy.

We traveled the U.S. off of the cash flow property and eventually made our way to Portland, ME before selling in the 2021 market.