Today, the requirement was reduced from a minimum of 4 units to 2 units. However, the complex must be either be approved by FHA or undergo the DELRAP Process (Direct Endorsement Lender Review and Approval Proces). The requirements for approval are also more stringent than they used to be.
For further information, see https://entp.hud.gov/sfohlp/f17cndprhlpp.cfm.
Here's a link where you can fin the FHA approved condo projects
And here's the link for an overview of the DELRAP (Direct Endorsement Lender Review and Approval Process)