How to figure holding costs on a long term flip you're living in?

[Bonnie Low]

My husband and I are Real Estate investors. We've flipped some houses and are used to relying on pretty standard formulas for calculating "quiet costs" and repairs and ARV to determine what our max offer should be. However, we're looking at a house that represents a situation we haven't dealt with before. We're looking at a house to flip that we actually want to live in for a couple of years. We plan on living there for 2-3 years until our son graduates from high school. Normally, we calculate the cost of the mortgage or hard money loan on the property, closing costs, commissions, utilities, insurance etc as our "quiet" or holding costs. However, it seems odd to factor in the mortgage, utilities and insurance in this situation as we would normally have these anyway and we'll be selling the house we live in now. How would you factor these costs into your holding costs to determine your maximum offer, or would you?