For completeness, I think this book is The Man Who Used the Universe by Alan Dean Foster. I have given a detailed description of the book in my answer to Story ID - ruthless criminal; legal/illegal citizen ranks.
To address your specific points, the rankings you mention are called class:
There were a hundred classes of citizenship, both legal and illegal. Of course, you could hold both, depending on your profession and avocations. Loo-Macklin was an eighty-third-class illegal and had spent two years in that status. He was tired of it. Any twenty-two-year-old would have been. But Loo-Macklin was very patient, which the average citizen his age was not. Patience was a prerequisite in his chosen line of work.
Loo-Macklin makes a deal with an alien race called the Nuel:
However, I have been able to persuade sufficient of the Heads of the Families (from his studies, Loo-Macklin knew that in Nuel society, a "Family" might consist of several hundred thousand individuals, a Great Family of millions) to allow me to make this contact with you. We occasionally find the rare human with whom we can work."
"Work how?" Loo-Macklin leaned forward, interested.
"I have what amounts to a business proposition for you, Kee-yes vain Lewmaklin. Would such coming from me interest you?"
At the time Loo-Macklin's deal appears self serving, but his ultimate aim is to (spoiler alert!):
Save both mankind and the Nuel from another warlike alien race called the Tremovan by bonding mankind and the Nuel into single unit strong enough to fight the Tremovan.