There was a story a while ago when IRS went after someone who was fixing their friends' and neighbours' cars and didn't ask for money in return. He was retired and he liked working on cars and he did it for free. IRS claimed he should have reported it as income.

In respect to money being a measure of wealth, was he "theoretically" becoming wealthy and acruing "good will". Later by changing his mind and asking for favors from his neighbors he could "cash in" his "good will" but avoid paying income and sale taxes on it.