This sounds like the "affiliate marketing" business model (earn a commission when you sell someone's thing). That business model is definitely alive and well!

I might have tried a service like you're proposing when our company was very small.

Now that it's bigger, we have revenue goals that we need to hit, and I wouldn't want to hire someone for free to help hit important KPIs. If a larger company does engage with this model, it would probably be to supplement an existing revenue stream I would imagine.

I think the biggest risk with the model you're proposing is that it's more appealing to small companies who are more likely to not have reached PMF yet, and therefore have products that are more difficult for you to sell compared to more established companies.