The Pharisees were a political party, so this is a bit like asking how Republicans earn a living.
Pharisees had a range of trades and professions. The apostle Paul was a Pharisee (and still called himself one long after his conversion — Acts 23:6), and he made tents (Acts 18:3). Other Pharisees were professional scribes (i.e., they wrote documents for people). Presumably they did most other jobs as well.
The Pharisees developed and controlled the synagogues while their chief rivals, the Sadducees, controlled the Temple. So Temple trade was probably operated and controlled by the Sadducees, as was the Sanhedrin (the Jewish parliament). However, there were plenty of Pharisees in Jerusalem and some were members of the Sanhedrin including Gamaliel (5:34) and Nicodemus (John 3:1; 7:50).