NPCs for business owners

Can anyone give me a general idea which deductions are often added back in with profile schools? Seems to me that one can estimate their income if they know what to consider, and make NPCs more accurate early on. I have two nephews that are starting this process this next year then my own son a few years down the road.

This varies by school. But think of the things others have to pay for anyway…cars, cell phones, utilities, food, trips, possibly even home office space…because that room would be in your house anyway.

That is exactly in line with what I was thinking and makes perfect sense. Thank you.