Microsoft Word is expensive, but it is also the de facto standard for writing and publishing. I urge you to use it if possible. Even so, consider these word processing options.
As an alternative to purchasing Word (or Office), you can check out Office 365. It includes Word, but instead of buying the software for several hundred dollars, you pay a small monthly fee. As a benefit, you are always on the latest version, and depending on the license, you may get to put it on multiple computers.
Other Word Processing Options
If you pick another word processor, make sure it can output files in a .docx format (Microsoft’s Word format). Always submit your work as a .docx file.
Scrivner, a popular writing tool designed for how writers think and work, is gaining popularity. It can also output a .docx file, as well as many other formats.
Another word processing option is Google Docs, but Microsoft Word remains the industry standard—and my recommendation.
In a related issue, consider using dictation software to write.