The cheapest most cost effective way I have found to run a node is to do it on a small form factor computer like a dell optiplex 9020. They have them on pcliquidations.com for around $140 right now. Sometimes they are cheaper. You might also consider getting a 2tb drive so it lasts longer as the blockchain increases in size.

You can run Bitcoin core on a Mac but sometimes you get a message blocking you from opening applications from an “unknown developer”. You can override this message in system preferences.