I want to travel to the USA by cargo ship from either Portugal or Spain. 

 1. Is it possible? 
 2. How much does it cost?   
 3. Is it possible that I can also have any job on the cargo ship while travelling to the USA, so that my travelling expenses can be reduced or waived?  

By the end of next month I hope to get my seaman book. However, I never had any experience of seagoing. I am a Pakistani national.