Hello,
You mentioned a printer that needs macOS 10.14. Any information about the exact printer model?
Apple's AirPrint technology (About AirPrint - Apple Support) as such works with macOS 10.13 High Sierra (and some earlier operating system versions), without the need for additional drivers/software, provided that the printer and the Mac are connected to the same network (Wi-Fi router). AirPrint supports wireless (Wi-Fi) or wired (Ethernet) network connections. However, a printer manufacturer may supply extra software (for example, for setup and ink management purposes) that requires macOS 10.14 Mojave or higher.
So, if the printer that you wish to purchase is an AirPrint model, it may be possible to use it (at least temporarily) under the existing macOS version, depending upon the printer manufacturer requirements and any ink subscription agreements, et cetera.