Whether SFR or apartments & commercial, portfolio lending and small banks are the key to long term financing.
We see lots of investors being turned by fannie (traditional mortgages) when they really need a portfolio loan (can be for multiple properties-blanket loans, single properties, borrowers who may have had foreclosure in last 3 years, ).
Portfolio loans are simply loans held by the institution after closing and are not insured or guaranteed by the government. May be a bank other institution.