The unethical part comes in when you're purposely padding your estimates, delaying response, feigning work load, or profiting from a side business. The last one depends heavily on your work agreement, state law, and how the company chooses to interpret things. I know of a guy who was outed by coworkers for doing side work, but after review, management decided it was fine as long as he wasn't using the work phone for side-work calls.
Of course, nothing is black and white, and rationalization is just as strong an intoxicant as overreaching corporate policies are.
Of course, nothing is black and white, and rationalization is just as strong an intoxicant as overreaching corporate policies are.