I would say a year is somewhat common, but that is not much time.

See https://www.biggerpockets.com/forums/432/topics/21...I also see no utilities, unless they are lumped into garbage.

Think about things like utilities, insurance, interest, taxes, typical consessions (seller paid closing costs for retail buyers), commissions, etc. - those things add up.

This is because you have to furnish and pay utilities that you wouldn't in a standard renting situation.

What are some of the most common tax related mistakes you see new investors make? 

House is in need of the following capex items soon....Roof/Gutters/Insulation and Third Electrical curcuit box (Common area).If I used a Heloc to fund the capex items it would take 4 yrs of investing all cash flow into paying of the Heloc.

Is this issue common?

Then we factor in utilities & setting money aside for payments, probably close to $900-$1000.

Utilize the BP calculators and find a reputable general contractor who has done several flips.

(I am guessing there are common problems with these type properties)