Is a 2009 iMac a1311 worth buying in 2020?

To save you lots of headaches make sure the seller has prepared the iMac according to this Apple document: What to do before you sell, give away, or trade in your Mac - Apple Support. If it isn't you may have a difficult time getting it to work at all. Also make sure you have return privileges if it doesn't work and pay for it by credit card so you can contest the purchase if the unit is not as advertised and not useable.

The fastest port that model has is Firewire 800 (800 Mbits/s) which wont be that much of an improvement over the installed drive: (Storage 500 GB, 1, or 2 TB (7200-rpm)). It might have the faster 7200 rpm drive which would be good. Just some food for thought.

I wouldn't get a 2011 model either. Its Safari version will load every website I know of but it's just a matter of time before yet another even more secure standard emerges. That, and the fact websites including those you may need to participate with online lectures and meetings have only grown more resource-intensive means there simply isn't much more economic life to what is essentially a ten year old Mac.

Get a 2011 model only if its really, really cheap, and plan to replace it in a year.

Besides, buying a used Mac is a task best left to very experienced Mac users, because nearly no one prepares them to be resold properly. Only Apple sells refurbished Macs. If you want to save some money that's the way to go.

Refurbished and Clearance

Apple considers 2009 iMacs as “Obsolete” and so should you. Many newer applications won’t even load or run on an 11 year old computer. This would include modern web browsers and that would make your computer and personal data at risk. You online meeting and university software may not work either.

Sorry, but it’s best to save your money until you can buy a newer used iMac.

That’s a model 12.1, a 21.5” screen, with Intel i5 processor running at 2.5 GHz, 500 GB spinning hard drive and base 8GB of Ram. The newest OS it will run is 10.13.6. This might barely do what you want.

The ram can be upgraded and you can add an eternal SSD for faster performance.

im only looking to do word processing, internet browsing and online lectures, teams meetings etc

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Those I underscored are not "low-impact" activities any more. Anything with modern video is demanding on hardware and often has higher macOS requirements that a 2009 Mac can support.

The other problem is that there are two 2009 iMac sub-models with very different capabilities One cannot be upgraded past Mac OS 10.11 and the other is constrained to no higher than OS 10,13. Current OS is 10.15 and a new version is due to drop within a month or two. You will run out of browser support at some point, particularly if you buy the "Early 2009" version.

If you already owned this computer I would be glad to suggest to ways to help it live longer but, as you are shopping, please don't get a 2009.

Absolutely not! It's a horrible purchase. If your budget is limited then buy a used one from a reputable source such Apple, they sell refurbished Mac that are identical to new, have the same warranty as new and are eligible for AppleCare and you can save hundreds of $$. In short, no downside.

If you still can't afford those, www.macsales.com sells used Macs and they come with a warranty. In addition Macsales goes through them and has awesome support.

The Thunderbolt ports weren't added till 2012.

This iMac disagrees:

Do you know what model 2011 iMac? Or the screen size (21.5 or 27) and/or the processor (i5 or i7)?

I believe the 2011’s have a Thunderbolt 1 port for 10Gbs. It should have a 7200 rpm drive as well.

The mid-2011 iMacs have Thunderbolt, which matches the OPs model number. Your screen shot is from a late 2011 which was the economical model.

If you want a 2011 iMac, then here you can also get a 2 year Warranty on it...

https://www.macofalltrades.com/shop/apple-desktops/imac/?_bc_fsnf=1&Year=2011

Thanks, never heard of the economy model ! 👍