If you have the port and money for it, I'd recommend a separate drive for the second OS. Windows is kinda notorious for stomping over GRUB if you rely on partitions for your dual boot.

If you're worried about installing to the wrong drive on accident, you can always physically disconnect the existing drive until install is complete, then plug it back in and set the boot order in the mobo config.

Honestly just get a second drive

You can run it from a live USB, which is also the install media. It's not persistent, so if it restarts, you lose data. It's a good easy to say last year it without making any changes. Like others mentioned, I wouldn't dual boot.

As other people have said, you have to be carful with dual booting on the same drive with Windows. It doesn't play nice with others. To add on though, Linux can access your NTFS (or whatever) systems fine*. You can leave them as they are and access the same data on both systems, though Windows is not capable of reading most other filesystems.

*May require installing a package, but every distro I've tried could out of the box.

I had an old computer and Linux is all that I installed. Not everyone is going to have an extra computer to do that with. However, this computer is more than 10 years old. It was quite good at the time, but it's junk compared to modern ones. Yet, it is more responsive than my very nice modern laptop that's running Windows 10. It's not going to beat a new computer in a race to solve a computational model, but for streaming, browsing, and day-to-day stuff, the lack of bloat means things open quickly and UI elements respond immediately. There is probably a fair number of people with computers they think are useless that would actually work very well with Linux.