What to do with possible clients that ask for free sketches?!

[vorenls]

Maybe all of our have had the bad luck to meet with possible clients that ask for free sketches so they can choose between the different freelancers. 
I am Graphic Designer and Illustrator and sometimes there are people that ask me [before we start a contract] for a sketch, so they can choose easier between the different applicants. The problem: They don't want to pay for it. So there will be many freelancers working for one project and only one will get paid [with some luck].
Maybe I am wrong getting furious with this situation, but when you go to a restaurant, do you ask to taste food,  and then if you like it you sit to eat?
So, what to do with this clients? 
Tell me your previous experiences 🙂
So, less of this kind of persons and more peace, pls!!!
Thanks for reading!
Leandro

[prestonhunter]

Leandro:
Real clients will understand when you say yes, you will provide sketches, after they create a contract to pay you for that work.

Scammers are never going to pay.

But you don't always know when people are a real client or a scammer.

So the thing to do is to ALWAYS be polite. Always communicate in a professional manner.

Give every prospective client an opportunity to do the right thing.

"George:
Yes, I would be happy to create those sketches. You can hire me using a temporary hourly contract to do that. Or you can use a fixed-price contract with a single $75 milestone in order to may for 3 original sketches of the McGregson design. Whichever you prefer is fine."

If the client hires you, then that's great.

If the client does not hire you, then use the "Flag as inappropriate" link button to report them for asking for free work.

[vorenls]

Great answer!
thanks Preston, I will take your advices! 🙂
Best, Leandro

[kinector]

Preston is 100% right.

Just adding a tip for avoiding those situations altogether.

Raise your rates. (I couldn't see your profile on my mobile, I have no idea what you're charging currently.)

Scammers and window-shoppers rarely target those who appear to master not only this site but freelancing in general.

Ever since I set the hourly rate to a 3-digit figure, I haven't been bugged by those who just want a free consultation at all.

Every connection made here is a real deal now.

The only category of people left to filter out is those wishful thinkers who are trying to get work done in a domain they know absolutely nothing about. Those deserve a free intro call to be scanned thoroughly. Some turn out to be great projects, some discussions just die off. Those are impossible to predict before taking some level of action. 😉

But of course, high rates must be justified, it's absolutely necessary to keep that in mind. Always.