Pages, Numbers, and Keynote can read/open Microsoft Office files and can also save in MS-Office formats (Word, Excel, Powerpoint). There may be a few options or formats that don't come through perfectly when doing these conversions, but for basic use, they work well.
There are other low cost or free options, such as LibreOffice.
If you want or need the full functionality of the MS-Office products, probably the best approach is to license MS-Office 365. I have a family plan license for 6 users, $99/year, which is pretty good on a per user basis., just $17/user per year. For a single user it is $69/year. You are kept fully up to date plus you get Outlook and some other programs plus 6 TB of storage (family plan; 1 TB for single user license).
Alternatively, you can purchase Office Home/Student for $150 one-time payment but you get a lower level version of just Word/Excel/Powerpoint and no cloud storage.
So you have several options that are zero cost, as well as others that range from one time $150 payment to $69/year for one user ($99/year 6 users).