Why do so many grocery stores give away free samples? Because they know you are far more likely to buy the product if you sample it first. Learn for free what these large stores paid to find out; free samples can increase your sales.
Just about any business can offer prospective customers a free sample, no matter what they are selling. Service businesses can do this just the same as retailers selling products. Most people are hesitant to try something new, but if you make it easy for them and they like what you are offering, you may have just converted them into a customer.