I might be mis-understanding the product, but…
if I’m not, then you want people to pay you for advice that might or might not result in more sales.
That’s going to be hard to sell.
It doesn’t help that your target audience doesn’t make much money (ebooks/courses, with few exceptions, don’t bring much revenue) and the risk is that they pay you and get nothing out of it.
If you’re confident that your advice would lead to higher sales, go into affiliate business.
Don’t tell people how to market and sell their stuff better, market and sell it for them and get a cut for every sale.
That’s much better revenue source than selling the advice once. You would capture much more of the generated upside.
It’s also zero risk to content makers as they only pay you if they also get paid.