[Darryl Ramm]

It is actually not hard, but you do need to think through a few things and be careful. And yes OK for a first time go at stuff like this might take a while, but once you have this sort of stuff done a few times it takes me ~1 hour to get a whole new boot disk set up.... assuming I have every installer ready to go.

Again I will reemphasize if you are not creating backup/clones today solve that right now. I highly recommend carbon copy cloner to external 7200 rpm HDD for backup.

The obvious question is if upgrade cost is an issue why upgrade macOS to Catalina? And if that was a mistake then just go back to Mojave (but which practically if you do not have a recovery backup you should do by doing a full clean install onto a spare partition or drive, testing everything out then cloning back over your boot drive).

Want to stay on Catalina... some dealers still seem to have perpetual upgrades they can sell... call around real soon if you do not want to end up on a subscription.