Which affinity-group financial institutions are known for precise eligibility rules and low-fee checking accounts?

Affinity-group financial institutions that are often known for clear, strict membership rules and low-fee checking accounts include:

• Credit unions tied to employers, professions, or associations
  Examples: teachers’ credit unions, government employee credit unions, military credit unions, university-affiliated credit unions.

• Community-focused or membership-based credit unions
  These often have very explicit eligibility criteria and tend to offer low-cost checking.

• Some “affinity” banks or banking programs linked to organizations such as alumni groups, unions, or professional associations
  These may offer special checking products with reduced fees.

If you mean institutions with a reputation for especially precise field-of-membership rules, credit unions are the clearest category. They commonly require membership through:

• employer
• profession
• family relationship
• geographic area
• association membership

And if you want, I can also give you:

1. a list of specific U.S. credit unions known for low-fee checking, or
2. a comparison of credit unions vs affinity banks for eligibility and fees.