I’m trying to buy a used Mac Pro 2007

It can only run up to MacOS 10.7.5.

It will not be usable in any meaningful way on the Internet, because most sites use httpS: and that Mac cannot be upgraded to do that..

It is not worth paying money for today.

MacBook or MacBook Pro 2007 or later model. 4GB will be slow, 6GB will be OK. These can be updated to 10.11 El Capitan as the last MacOS they can ever run. This gives access to httpS: sites, which you will need.

The older the model you choose, the less upgradeable and the more "disposable" it will be.

If you choose a 2011 model or later, it can be upgraded further.

This is the forum for the Mac Pro that looks like this:

Do you want to talk about that---^

Or do you want to talk about MacBook Pro--v

Which?

OK, what do you want to do with this Notebook computer?

What kind of future for expandability does it need to have?

Do you have an iPhone or iPad as well?