Cash on cash calculation question

[Pearce G.]

Let's say I'm flipping a property.  My all-in acquisition/repair/holding cost was 80K.

Ignoring selling costs, let's say I sell it for 100K with seller financing.  And I require 10% down with the rest financed at 5% with a 10yr amortization.

What is my cash on cash return?

Is it simply the 25% markup + 5% interest = 30%?

Or is it a calculation of total annual payments divided by net all-in costs?