[moocow01]

Your missing another big one which is the cost to hold the house. If you're an average flipper that investor money is going to cost you about 1% per month of the purchase price so you can probably assume another 3% or so there.

After that you need to factor in your time as the flipper (time to do the purchase analysis, acquire the property, fixup the property, market the property, sell the property). Ultimately for flippers a 15% spread between purchase and sale would usually be a sizeable loss