When you give your time or services away for free out of obligation or unwillingness, then you are blocking the flow of money or abundance to you because you are affirming to the Universe that your time and services are worth nothing. And the flow of abundance is also blocked for the other person.
But if you choose to give your time and services for free out of the goodness of your heart, then go ahead and do so. Only give if the recipient is going to benefit and grow in some way after receiving what you give to them, versus giving to someone who will just take from you and not benefit at all.
Listen to your heart and do the things you choose to do, for unlimited abundance will flow naturally into your life.