To file the PERM Labor Certification application, the U.S. employer needs to obtain a Prevailing Wage Determination from the State's Department of Labor for the alien employee. This Prevailing Wage Determination establishes the required minimum wage for the job position. It is better to obtain the Prevailing Wage Determination prior the employer to start the recruitment process.

Obtaining the prevailing wage before recruitment process beginning can avoid many potential complications. The employer should obtain Prevailing Wage Determination before the recruitment process for the position beginning, to avoid if the alien employee's wage in the recruitment process is lower than the actual Prevailing Wage Determination issued by the Department of Labor of your state. 

Also, the PERM Labor Certification should be filed during the assigned time period of the Prevailing Wage Determination, thus the employer should obtain the Prevailing Wage Determination before the it starts the recruitment process, to avoid the Prevailing Wage Determination expires, or have to start the entire recruitment process again.