I’m not really sure what to do then. You might have better luck asking on the Mint forums.

Separate drives is safer since Windows might overwrite the bootloader when it updates. If you can’t do separate drives, then you want the second option on your screen right now.

Are you using a single drive for both operating systems or giving each their own drive? If it’s the former, then it looks like you’ll have to manually shrink the Windows partition and then create the necessary partitions for Mint.

Some manufacturers have outlets for refurbished devices. They’re not like bargain bin prices, but it’s something.

There’s also a lot of electronics recyclers on eBay. I’ve haven’t had any bad experiences there.

You could also try going to local thrift stores. Don’t bother with Goodwill though. They put all their good stuff online. Unless you live near one of their dedicated electronics stores, like the one in Tallahassee, Florida.

The only other option I can think of is checking out something like Facebook Marketplace or Craigslist. Unfortunately, you do need a Facebook account for Marketplace.