A marketing company (often a broker pretending to provide leadgen) will deliver leads and simply share in the commission made by those write the business. These unscrupulous marketing businesses normally promote the service as 'risk-free' because "we do all the work", when in actuality it's a very high-risk model since these companies are not actually introducing assets into your business that'll continue to deliver value to your operation (in fact, they're providing a service my 8-year-old daughter can perform more effectively). The service is one predicated on taking advantage of the general perception or illusion that lead generation is a difficult endeavour... when it is not.
There's no such thing as "inheriting all the risk" when there's little to no risk to start with. What the model does do is introduce worse-practice and technical debt into your operation, and you'll share a commission with somebody introducing a bottom-of-the-barrel marketing model to your operation when higher quality leads could have been generated by you for a tiny fraction of the cost.
There's a good reason we don't engage with profit-share arrangements: they're grossly inefficient from a business perspective, and they're often non-compliant in structure and execution (with the originating business usually bulk-sourcing traffic, recycling FB pixels, and introducing ridiculous quizzes into your funnel designed to 'qualify'... or erroneously disqualify). Instead, we provide simple systems designed to turn your entire operation into one that supports its own extremely powerful lead generation and marketing efforts.