I won’t include them in the costs since they should increase the value.I will also be careful of property managers who mark-up maintenance costs in addition to their regular fees.

This would include everything but the land...including well, septic, power, driveway, clearing land, grading, foundation.  

What is the monthly payment to include taxes and insurance?

Plus, taxes seem to range a bit.I've heard @Brandon Turner talk about including property management with your analysis from the start, so you can easily start using a property management company and not impact your original pro forma estimates.  

Include in the closing papers that the house will be empty and in clean swept condition.

I include another month of holding costs in my projections to accommodate extra time needed to close on the pre-sale.  

Hi,We bought a triplex in March with 25% down payment. since then we've added a brand new roof, redid first floor bathroom.

I am brand new to Real Estate and I would like to learn more about investing in this area.

I'm assuming that the other half of the mileage can be deducted once the second unit has been placed in service, but I can't seem to find a definitive answer on if mileage can be included in start-up costs.2.

You should include management fees, even if it's self-managed.