What are cheap ways to test interest in a b2b app?

Anyone got a good link/video that will tell me about market testing? I have an idea and i would like to collect email addresses and see how much interest there is in the idea (it will be an artist marketplace). I'd like to target these artists to see if they would be interested in the market place by collecting email addresses.

Do I buy keywords/facebook ads in order to generate leads like this? I don't want to spend a ton of money but i do want to test the idea.

Find out where your target audience hang out online/offline and ask politely.

cheap in terms of cash: go out of the building and talk to them in person
expensive in terms of cash: run ads against a landing page of your idea

Not sure what your "time" is worth, so i'm leaving that out of the equation.