New Construction Expense Calculation

[Peter Schuyler]

Im looking at a new construction Duplex unit, will take 6 months to build.

In all the reading and research the 50% rule for all expenses to me seems high for new constrcution.

I'm assuming 

• Expense will be Taxes, Repairs, Capex, Vacancy needs to be saved per month for expenses, but 5% for repairs, and another 5% for capex seems a bit high on a new Duplex, I do not want to kid myself, but I plan on holding for 3-5 years, so Im hoping no roof failure, or appliance failure 3-5 years, and first year is builder warranty
• Utils will be picked by owner
• No HOA, PM will be done by myself

Does anyone have an alternate percentage for new construction buy and hold 3-5 years.  Roof- A/C units should last 3-5 years I would think, and only minor repairs to window coverings, etc.

Looking for real world expense experience with new construction.

Thanks