iMac 2011

Maybe.

What do you need it for? Does it come with any RAM/SSD upgrades? How cheap can you buy it? (rhetorical questions)

2011's are still capable of basic tasks and have aged well (with the exception of 6970M models), but they have aged, are stuck with USB 2.0, and are starting to have software compatibility issues.

It could be a good purchase if you need a dedicated machine for legacy 32-bit mac applications.

It could be bad if you need it to run the latest version of specific software.

Otherwise if you can substitute FireFox for Safari and OpenOffice for Pages/Word... what is the oldest version of MacOS you could see yourself still using today? The oldest I'd recommend is El Capitan which would suggest 2-3 years of life remaining with minor upgrades. Is the price cheap enough to justify such as short remaining life?

I used to have an iMac 21.5 from mid-2011 until I stopped using it 3 months ago. It still functions perfectly as Apple keeps giving security updates for Safari etc. However, a lot of latest software isn't supported on High Sierra. If you are only using iMovie, it would be fine when you upgrade its RAM to 16 GB. It is a truly fine computer and it is worth buying unless you want to latest software.

it will not support newer macos versions

and think apple are stopping support for high sierra

and microsoft also only support 3 macos versions back for newer software

That would depend on what you intend to do with it and how cheaply you can get it.

In general, though, I'd have to say no.

Moraswi wrote:

Could I upgrade the software to El Capitan without issues?

FWIW, High Sierra is newer than El Capitan. El Capitan would be a downgrade.