Depends on a lot of things... like are you talking some backwater town in Louisianna. Or are we talking Beverly hills or Long Island? And what are you cleaning up... a HazMat site... a crime scene, or someone's house?

I agree with Smooth you have to give us a lot more information as many things apply;

Type of account to be cleaned.

Density of the 15,000 sq ft.

Location (As Smooth said)

What type of flooring.

Are windows included.

Is it regular cleaning or is it a construction clean up and thus a one time clean.

Give us more info please.

Stringer

A spa salon with daily cleaning and 15,000 square ft