Mac Mini setup

If the 2009 iMac is 27" it should work as a display. You would need a USB-C to Mini DisplayPort cable.

https://www.apple.com/shop/product/HN8B2ZM/A/mophie-usb-c-cable-with-mini-displayport-connector

Use your iMac as a display with target display mode - Apple Support

The "Mac from 2019 or earlier" part doesn't seem to apply for Mini DisplayPort iMacs, such as the 2009 iMac.

11cch20 wrote:

If I buy the new Mac Mini M1 and use my 2009 iMac 27" as the display will I be able to utilize the mini as the operating system, exclusive of the iMac? In other word just have the iMac be a display.

No. 2020 and later Macs inlcudingh the M1 Macs do not support Target Display Mode. Apple has chosen to not continue that feature with newer Macs.

No, you don't absolutely need an iMac display to do photoshop.

Depending on your budget for the display:

https://www.amazon.com/LG-27UK850-W-Monitor-Connectivity-FreeSync/dp/B078GVTD9N/ref=sr_1_1?dchild=1&keywords=4k+display&qid=1605210869&sr=8-1

https://www.amazon.com/BenQ-PD2720U-Thunderbolt-Reproduction-Professionals/dp/B07N4M92P1/ref=sr_1_13?dchild=1&keywords=4k+display+USB-C+photoshop&qid=1605211036&sr=8-13#

https://www.amazon.com/Dell-Ultrasharp-U2718Q-27-Inch-Monitor/dp/B073VYVX5S/ref=sr_1_14?dchild=1&keywords=4k+display&qid=1605210869&sr=8-14

No. IT, but I do have Photographer friends. So I've picked up a few things in relation to Photoshop and displays since I help them with their Macs sometimes.

Most of them swear by the BENQ monitors.

You are very welcome. Excellent photo. Congratulations.

You can always just buy a monitor and connect it to the Mac Mini. Not sure why it needs to be an iMac display.

Even a cheap entry level monitor today will have a better display than a 2009 iMac.