A few things to consider: both C and S Corp require payroll. That isn't a "savings" as many people think of it. That simply shifts costs from the individual to the entity, and since you have only the one person, it's still "their" money = no real savings. C Corp is double taxation, in that the entity stands separate from the Shareholder (not Owner) and is taxed, via the Form 1120. It would matter if real estate is involved; it is not recommended that an S Corp hold real estate.

And you stated this is only 1 person, so there should be an analysis for why to even consider being an LLC and why to elect to be treated as an S corp. You don't need to be an LLC in most cases; there are some professions where that is required.

In other words, every entity type has its positives and negatives and you need to know the reasons for each, then see if this person's activities fit into any important provision that makes the difference.