Any bank may purchase and own stock and capital notes or other evidence of debt issued by a mortgage banking company, or its affiliate, the principal business of which is the extension of short, intermediate or long-term credit to individuals, partnerships and corporations, which credit is secured by real estate mortgages. A bank shall own at least eighty percent of the stock of any such mortgage banking company and may not obligate more than thirty percent of its capital stock and surplus and undivided profits for such purpose.
SDCL 51A-4-28