There are basically two approaches:

• Social media agencies that manage company accounts on behalf of their clients and have their employees produce content for them.
• Agencies that operate their own accounts, which are financed through product placement, e-commerce (mostly dropshipping), or affiliate marketing.

Typically, these companies pursue both approaches simultaneously.

What they offer the actual content producers, i.e., the (sometimes even pseudo-self-employed) employees, is the following:

• A salary or at least project-based remuneration.
• A network of contacts to advertising customers and thus lucrative sources of revenue that are pretty much unattainable for individuals without significant reach.
• A network of contacts to other “influencers” in order to gain subscribers, etc. through strategic cooperation
• Professional equipment (cameras, dongles, drones, video editing applications and so on)
• In some cases, substantial advertising budgets for ads to promote new accounts (performance marketing) and, in the case of campaigns for external clients, “seals of approval” from meta (“Facebook Partner” for example — these seals are only issued to companies who spend a significant amount on advertising on the respective platform).
• Opportunities to collaborate with other employees of the company, which can also create network effects.

There are certainly other advantages, but the key point is the contact with advertising customers, i.e., companies that want to engage in social media marketing. These contacts are only accessible to private individuals if they already have one or multiple successful accounts, which unfortunately only very few of those aspiring to a professional career in this field ever achieve.