Not quite sure if you mean use the 'Word' programme or just anything to write into.
Assuming the latter, I have happily used pages for years. It's not too difficult to set up and while there are a few limitations, they are not enough to cause major problems.
Remember, at the very start of any writing project you need no more than pages to write on. It's only when it's finished you need to work it into presentation form.
Then, if you pose the right questions in the 'pages' columns you may be fortunate enough to attract the attention of the gurus in that subject.
You,also, have a free text writer/editor on your iMac, already. It's in your Applications folder. It's called Text Edit.
If you looking for something simple to use right away.
If you are looking for something a little more robust.
Here are some free alternatives.
On the cheap,
Print Shop Pro