He must have already filed at least as a sole proprietorship. The first benefits to becoming an LLC or an S-corp is the liability limitation: it lets you distinguish between your assets and the business's assets in a legal sense, so you don't (for example) lose your house because your company gets sued. The next benefit is business-related tax deductions. This goes hand-in-hand with business-related tax complications, so if he isn't planning on taking deductions and can't see a legal need for separating his business assets, it might be amounting to a more complex (and therefore expensive) tax situation for no tangible benefit. Of course, other things he may decide to do (such as hiring employees or issuing stock) could force him to incorporate.

I'd be surprised if it didn't make more sense to become at least an LLC, but tax law is complex. If I were him I'd do whatever my accountant told me to do.

LLCs act as pass-throughs, distributing profits (and thus taxes) in proportion to ownership stakes. As a presumably sole owner of an LLC, he'd have to file a Schedule K-1 with the company tax return, which essentially moves the profits of the LLC onto his personal tax return (which is then taxed accordingly).

I suspect Ze has some form of corporate entity. But that is unlikely to change the taxable nature of the income unless it's a designated non-profit organization.