They can be free, depending on the system. For example, in moneyless societies (anarchism comes to my mind), you don't have to pay for a thing because the concept of payment doesn't make sense.

Anarchism isn't an economic system no matter how much socialists want it to be. So its not really a good idea to introduce it as one. On top of that not every anarchist is a collectivist or socialist so what you're describing is communism. And Lenin tried going money less. It would've been a cute little experiment except that we can't ignore the piles of corpses it produced from starvation and lack of basic resources. ( many of those corpses were Slavic btw). 

And what if medical professionals want to get paid? What do you say to them? Do you merely force them to accept what you want?