Starman Jones by Robert A. Heinlein
Paperback. Condition: Good-. 1978. Del Rey. Seventh Printing. Stock Image.
When his step-mother marries a no-account man, a country lad joins a hobo and together they fake their way into the Space Stewards, Cooks, and Purser's Clerks brotherhood to get an opportunity for space travel in an age when only the wealthy are so privileged.
Book #7 in Heinlein's Juvenile series.