You can find legal, sealed copies of QuickBooks Desktop 2018 on eBay or Craigslist. However, remember: You are buying a data-entry tool only. Never buy a "digital download code" from a third-party seller—99% are stolen or fake.
QuickBooks Desktop 2018 is no longer supported by Intuit as of May 31, 2021 quickbooks desktop 2018 download free
When searching for "free downloads" of older software, users often end up on "crack" or "warez" sites. This is the biggest risk factor. You can find legal, sealed copies of QuickBooks