free medical advice ailments lawyer

A doctor and a lawyer were talking at a party. However,their conversation was constantly interrupted by people describing their ailments and asking the doctor for free medical advice.
After an hour of this,the exasperated doctor asked the lawyer, “What do u do to stop people from asking you for legal advice when you’re out of the office?”
“I give it to them”, replied the lawyer, “and then i send them a bill”.
The doctor was shocked,but agreed to give it a try.
The next day, still feeling slightly guilty, the doctor prepared the bills.
When he went to place them in his mailbox, he found a bill from the lawyer.