This is something like asking if there are developers who will do a mockup interface/database schema/class structure for your web app for free, so that you can choose the best one before the application is developed. You can probably find some people willing to work this way, but they probably won't be very experienced, as the experienced people will have figured out that it is hard to earn a living wage this way.
For logo design in particular, the initial design can be the hardest part of the process, so it doesn't make sense to give it away for free.
For logo design in particular, the initial design can be the hardest part of the process, so it doesn't make sense to give it away for free.