A doctor and a lawyer were talking at a party.

As they talked they were constantly interupted by people describing their health problems and asking the doctor for medical advice.
After an hour of this the doctor asked the lawyer, «What do you do to stop people asking you for legal advice when you’re out of the office?»
The lawyer replied, «I give them the advice, and then the next day I send them a bill for the advice. They pay the bill, and never ask me for advice outside the office again.»
The doctor was shocked but decided to try it.
The next day while the doctor was preparing the new bills the postman pushed a letter through his letterbox.
The doctor opened the envelope and inside found a bill from the lawyer.