Cannot recall what you call organisations in the US whose primary purpose is to provide mortgage finance for folk to buy their house. But that is/was the function of a Building Society. Originally a not for profit mutual "society" owned by its members (lenders and borrowers) which paid interest to its depositors and lent money out against the surety of the house purchased.
Concept is now severely watered down - many more suppliers of finance such as banks and some building societies like the biggest, the Nationwide, have become virtual high street banks. All feeling the negative impact of the collapse of the sub-prime market in the US.