Gainful employment
The ATO defines gainful employment as being employed or self-employed for gain and reward in any business, trade, profession, vocation, calling, occupation or employment.
That means working and getting paid for it.
This does not include voluntary work and rarely includes earning a passive income or ad hoc income of a domestic nature, such as being paid to house-sit for a friend.
You don¡¯t need to receive the income directly to be classified as gainfully employed; you can choose to salary sacrifice part or all of it.