Union Pacific Corp. is hanging out “Help Wanted” signs for train crew employees working out of its Denver office — and offering a $20,000 signing bonus as well. Even better? It’s an entry-level job, “no previous experience required,” for a job that could be paying up to $60,000 by the end of the second year on the payroll, depending on the hour worked, according to Union Pacific (NYSE: UNP). “These are the folks responsible for moving trains (engineer and conductor, and within…