Which of the following is considered an example of a direct cost in real estate?

A direct cost in real estate refers to an expense that is directly attributable to the development or operation of a specific property. In this context, a site supervisor is a direct cost because their salary relates specifically to overseeing the construction process or property management. This individual plays a crucial role in ensuring that the project stays on schedule and within budget, making their cost directly linked to the property being developed or managed.

The other options represent indirect costs or costs that are not directly tied to a specific project. Property taxes are considered an operational expense that applies to a property once it is owned, but they do not correspond directly to any single construction or management task. Marketing expenses may support the selling or leasing of a property but are not a direct cost of the property itself. Loan interest could be classified as a financing cost associated with borrowing money, but like property taxes, it does not have a direct link to the labor or materials involved in the project at hand. Thus, the site supervisor's cost directly supports the immediate functioning and success of the specific real estate endeavor, making it the correct answer.