In many parts of the country, credit unions act like banks and directly compete with other financial institutions. This means they offer all kinds of services and loans, including mortgages.
Credit unions also are found in all sizes and shapes. Some are private, while others operate as public institutions. Some credit unions do not offer mortgages but do offer loans that are secured by real estate. These home loans might be called second mortgages (they are second to the primary mortgage) or HELOC (home equity line of credit).
Just like banks, mortgage companies, and insurers, credit unions are likely to have some loans go bad from time to time. When that happens, they may have properties for sale.
Develop a list of the credit unions with offices in your investment area. Contact those credit unions and find out who operates the REO office. With smaller credit unions, the REO office might be just one person. Making personal contact at a credit union office will usually provide you with the contact information that you need.