To save expense of upgrading software, it may be possible to run an older OS than the OS your Mac came with.
I have a $2,000 scanner, but the driver only works with OS 10.6. In 2013, I replaced my mid-2006 iMac with an Apple refurbished mid-2011 iMac with OS 10.8 pre-installed. At the time there was no scanner driver available for OS 10.8.
On the refurbished iMac, the installer for OS 10.6 would not run. It gave a message something like "Sorry this software is not compatible with this Mac". However, if OS 10.6 was installed on a partition or external drive using an older iMac, and then that partition or external drive was moved to the refurbished iMac, OS 10.6 ran with no issues on the refurbished iMac.
Now I use an OS 10.6 partition on refurbished iMac only when I need to scan something. When I am not scanning, I start up from my OS 10.8 partition for all my other applications. (The scanner manufacturer has finally released a driver for OS 10.8 . . . but wanted $450 for just the driver.)
I am reluctant to upgrade past OS 10.8 as Adobe CS5 software may then not run. Upgrading Adobe software is beyond my affordability, so I am hoping I will be able to run OS 10.8 on a newer iMac when I need to replace the refurbished iMac. As a graphics printer, I've been using Adobe/Aldus software since 1988, and don't want to switch.