Attorneys vary in what and how they charge. Attorneys can charge an hourly rate, a flat fee for their services, take a percentage of a settlement amount (called a contingency), or a combination of these. Many attorneys will ask for a retainer (an amount up front), which they will bill against as they begin to work on the case. Once the retainer gets below a certain dollar amount, the client will be required to replenish it.
Many potential clients ask about a lawyer taking a case for no money up front and accepting a contingency fee at the end of the trial if they win. However, this is not very common with employment cases because in every employment case the majority of the work done by the attorney is done up front. An employment attorney spends the most time and money within the first few months when the case is filed in the proper forum, and there is no guarantee that the case will result in a financial settlement.
If you have financial issues, it is best to bring them up when you first speak with your attorney. There are times when an attorney can make certain adjustments, like taking on only a part of a case, in order to keep the bill down.