When you write for someone else who pays you just for your efforts and has claimed over the content you created as per your agreement with him, it is ghostwriting. In other words, it's like conceiving a surrogate baby whom you can't claim. However, you needn't get tensed about this aspect of ghostwriting because it is a vast niche today and there are scores of people all over the world who are doing it day in and out.
Take the case of the vast and fast-growing digital marketing industry. Depending on the size of their operations, these online businesses upload huge quantities of content every day, written by ghostwriters known as content writers. Yes, content writing is a form of ghostwriting, in case you didn't know it.
Many people including many content writers aren't aware of the fact that they are actually ghostwriters. Like I said, it's a fairly large industry with an enormous scope but because of the proliferation of a large number of non-specialized people into the digital marketing industry, the level of competition has risen higher and affected wages.
Outside the ambit of the digital marketing industry, ghostwriting has good demand among academicians, researchers, and other professionals who don't have time to write their papers. These individuals are always on the lookout for good writers who can ghostwrite their papers.
Within the academic niche, undergraduate and postgraduate students in many English speaking countries like the United States, Canada, UK, Australia, and New Zealand are always on the lookout for ghostwriters to write their theses. It is a stable career for someone who knows how to find enough work that pays for his sustenance with a little more to spare.
However, it is hard work with no respite and you only get paid for the amount of work you do; nothing more. You will have to be patient with the income you'll be earning, which isn't much compared to the amount of workload you handle but if you know how to set your timetables and have a steady source of work, it is a viable career for people who are blessed with powers of concentration.