An “Area Approved for Business” (AAFB) is the geographic area in which a lender’s home or branch office is permitted to originate or underwrite FHA mortgages. The AAFB is subdivided into HUD Field Office jurisdictions.
All branch offices registered by a lender will initially be granted a nationwide AAFB. The branch may only exercise its authority to originate or underwrite FHA mortgages in those states where the lender fully complies with state origination and/or underwriting licensing and approval requirements.
For additional information see Handbook 4000.1 I.A.4.b. available at https://www.hud.gov/program_offices/administration/hudclips/handbooks/hsgh