You can learn a lot from YouTube but how much trust would you put in a new hire when you ask them "can you do this job" and they respond, "eh, I'll look it up on YouTube"?
In this way you know the person has been trained to clean. At least in theory. Reality might be quite a different thing.
As for on the job training few companies have either the time or inclination to do so. Mostly because, I spend my time training you to do the job properly and you quit and go to another company to use the skills I just taught you.
Some companies that do train are starting to say if you quit in less then six months to a year after your training is complete you will be billed.
No, you don’t trust that they learned the skill on YouTube. They learn the skill on a video ( doesn’t have to be YouTube). Then when they apply for the job you give them the equipment and watch them do it in real time. Inspect their results. Give constructive criticism and explanation as to why this or that is important - then watch them do it again. Trust, but verify. A small business can succeed in this field. A bigger business will probably have quality controls like supervisors who check in from time to time - necessary because the client will pull the contract if it’s not done right.
It’s not complicated work, but could be hard work to clean an entire building as a full time job. In any case it shouldn’t cost $560 to learn it. And that’s just for toilets. How much does mopping class cost? Sink cleaning? Dusting tables? Safety protocols? $560 to learn to clean toilets - that’s about a weeks pay, at least even here where minimum wage is $16.90 an hour. Pardon the pun but that stinks and smells, like a scam. A certificate course in toilet cleaning. Imagine if the state forced licensing.