Ghostwriting used to be a classy profession. We were the ones, usually in a stealth mode, who wrote those important books and, later, opinion-editorials for presidents, presidential candidates, captains of industry, and the newly famous. In return we received generous compensation. It wasn't enough to get rich but the work was stimulating so we didn't grouse.
Now, because of digital, ghostwriting has become a career path even undergraduates at third-tier schools can pursue. Ads on Craigslist provide assignments for ghostwriting blogs for $10 each and pattern letters for direct mail at one cent a word.
The only way not to enter the newly constructed ghetto is to only accept assignments which pay decent money. Yes, just say "no." If you are going to be paid peanuts in the beginning, no matter what kind of wonderful work you produce you are not going to be paid a whole lot more. Not by that client. That's just how the game operates at the low end. Moreover, the creeps treat you terribly.
The high end is the only place to be. There the work is also intellectually stimulating. The clients are smart enough to treat you well. And there could be big bonuses and stock options.