First, whatever deals you find, I strongly recommend getting an Office 365 Personal subscription instead. With $69.99 / €69.00 / £59.99 / AUD 99.00 a year, you get not only the latest Office desktop apps, you will also get 60 minutes free phone calls from Skype to landlines in any country, and mobile numbers in selected countries, and more. You will also get 1 TB of OneDrive storage.
Or, if you want to share Office with your family and friends, you can get 6 licenses with $99.99 / €99.00 / £79.99 / AUD 129.00 a year. You and 5 other users have all the benefits Office 365 subscription offers. You will always have the latest Office apps; when Office 202X will be released, you will be automatically upgraded.
Read more:
Compare All Microsoft Office Products | Microsoft Office
Please notice, regarding the terms, that Microsoft has not updated the above linked page. Since October 2018, O365 Personal and Home subscribers can now install Office on unlimited number of devices, as long as no more than 5 of those devices are used online at the same time. More about this change in O365 terms:
Office 365 Home and Personal getting new device limits
That being said, you can use OneDrive safely from any device. Just remember never to save credentials when signing in:
As only pure 100% idiots with IQ smaller than their shoe size use online services without 2FA (two-factor authentication) when it's available, you will also be asked if you trust the device or not. Remember not to mark device as trusted, if it's not yours:
When done with OneDrive, close the browser. Notice that closing a tab is not enough, the credentials are still remembered and re-opening tab gets any user automatically signed to your OneDrive. Closing the browser however forgets your credentials, any successive sign-in attempt to OneDrive will again ask the credentials.
Kari