Hey @ShaylaWalker ,
Thanks for posting on the Instructure Community!
There is no limit to how many users you can have enrolled in your Canvas course. I am aware of some courses that have hundreds of people enrolled. When it comes to removing their access, if you're looking to purposely lock them out of the course, I recommend using course start and end dates, and ensuring you have the option where students are unable to participate / access the course after or before those dates are ticked on via your settings. You can also create different sections and provide each section with their own unique start and end date. However, if you're planning on using Canvas year after year, I recommend creating / copying a new course so those users aren't enrolled into it. Manually deactivating or deleting user enrollments can be very time consuming, depending on the amount of people you have in your course.
I hope this helps you out, please reach back out with any additional questions you have! We're always happy to help. Thanks!
All the best!
Noah