Every service I know of explicitly bans this practice, so unless you can employ the cleaner full time then if they accept your arrangement they risk getting fired.
If I'm not mistaken, services like Upwork and Fiverr will look at certain metrics for outliers, like repeat business in a particular industry. And for eBay, I think they’d look into cancelled bids on high-value items and check messaging history.
Disclaimer, based on old memories