Question about impact fees and when they're due on a building project with 2 phases.

[David F.]

I plan to raze a house I own in SD county and build a quadplex on this one parcel.  I've discussed with the county phasing the buildout in 2 steps, building 2 units at a time.  After those 2 are occupied with tenants I'd proceed to build the other 2.  

My question pertains to impact fees.  I understand they are due when the building permits are pulled.  I can't get a straight answer from the county.

Does each unit have its own building permit that would be pulled?

If so does this mean I would pay the impact fees on 2 separate occasions when each pair of building permits are pulled (even though all 4 units are on one parcel) or do I have to pay for all 4 at once?  Thanks in advance.