Is your claim that every photo will be labeled as AI-modified, or that people won't label AI-modified images? If the latter, just penalize the listing agents. Trivial.
The entire issue is that the platforms are already inundated with misleading, unlabeled AI-modified images.
Just like every Web site has a cookie warning.
It's very unlikely to be trivial though because the state typically lacks the resources required to enforce things like this at scale. You'll need to find violators, meet a burden of proof that they violated the law, notify them, give them the right to defend themsleves against the allegation, etc.
They'll almost certainly spend more time and money on the process than is ever collected if this ever happens.
The point of regulation isn't for the state to turn a profit. In fact, I'd go as far as to say that regulations that drive a monetary profit for the state are generally bad because they create a perverse incentive. For example, municipal governments adversely affect traffic flow by lowering speed limits because those lower speed limits generate more ticket revenue.
You could create a private right of action for this, but that is its own bag of worms.
Seems empirically false given e.g. the immense investment we make in counter-drug enforcement.
I don't know about the US because the US is weird, but:
* at 30kmph the rate of fatalities in case of a car hitting a pedestrian is basically 0%, at 50kmph I think it's 5% or more
* at 30kmph collisions are much easier to avoid due to the increased reaction time and the decreased braking distance (I don't remember the exact numbers)
* at 30kmph you can hold a conversation at normal speech levels next to a moderately busy road, at 50kmph you will have to shout (and not even notice it due to the high ambient noise)
Etc.
2. The burden of proof/right to defense/notifications etc are all quite a lot easier for licensed entities like real estate brokers – that's kind of the entire point of licensure