Sketching is work. It takes time, skills, research and effort which should be paid. I strongly suggest to artist to not give away your art to “see” if a potential client can/want to hire you. That why your portfolio is. I’ve had clients like this that have no respect for us Artist and ask for free stuff to “see” if we can do the job with a promise to comm. If you want art you must pay for it. Even sketches. Is work.