Ask your prospective employment law professional their fee structure, and how long they expect to have to work on your case. Depending on the issue, it may be better to work on a per-case basis rather than a per-hour basis. Both options are usually available.
Our body of employment law is there to help both the employee and the employer, so neither should hesitate to take advantage of it. But keep in mind that some aspects of it are there to protect the general public's interest, and that the government can use them against you if you don't follow all the rules.