Interesting, it seems like this might be a UK vs US thing. All the non-dodgy UK results for "income" I found agree with what I thought e.g. "Income less Costs = Profit" [1]

The one exception is HMRC (UK equivalent of IRS) which, for the purposes of corporation tax only, defines income like profit [2] (with some technical differences, but the same spirit). But for other purposes (e.g. personal income tax) even they use it to just literally mean cash received without subtracting off outgoings.

Using it in this net sense seems very odd to me, but maybe that's because I'm British. "Income" and "outgoings" look to me like symmetrical terms, and no one would consider outgoings to be after subtracting off money coming in (would they?!)

[1] https://www.cheapaccounting.co.uk/blog/index.php/income-prof...

[2] https://www.gov.uk/hmrc-internal-manuals/company-taxation-ma...