If anyone wants protection from a nanny, state or otherwise, they can pay for it. Offer all the certifications at the state level you want, just don't interfere with my ability to do business with anyone I please whether they're certified or not.
>society has an interest in providing minimum safeguards.
Requiring you to work at below market rates for YEARS is not in the best interest of society. Harming the poor or immigrant workers by not allowing them to earn a decent living is not in the interest of society. All of these things are in the best interest of the incumbent wealth, not "society."
If you want some protection, then you can easily pay for it. Hire a contractor through Home Depot, Sears, or some other trusted industry name where you'll get lots of contractual protections and the benefit that a multi-billion dollar corporation wants to keep a good reputation if it wants people to keep doing business with it. This works much BETTER than taxes because everybody DOES get to pick and choose where their money goes.
>These solutions are intended to solve collective action problems, which by definition cannot readily and consistently be solved by everybody acting independently.
These solutions are intended to maintain incumbent wealth which harms the poor. You keep trying to sell me on you protecting me, which you obviously know I don't value, without addressing the fact that your ideology keeps the poor in their place. There's two wealthy groups you're protecting here. First, as the property owner, I'm almost certainly more wealthy than the laborer. And secondly, you're protecting the wealthy incumbent workers who don't want lower skilled workers undercutting them.