2008 iMac and Mountain Lion

I am looking at purchasing a 2008 iMac from someone and from what i've read it may or may not work well with Mountain Lion (which has been installed). Are there any known other problems with buying an older computer like this? It will be for my 6 year old to primarily play games from the app store and the occasional internet web site. Here are the specs:

Intel Core 2 Duo 2.4 GHz
4GB DDR2 SDRAM PC2-5300
500GB Western Digital Hard Drive

Interface Type PCI Express x16
Graphics Processor / Vendor ATI Radeon HD 2600PRO
Video Memory 256.0 MB GDDR3 SDRAM
Video Interfaces DVI
Max Monitors Supported 2.0

Thanks for any help!

No real 'known issues'. Only the usual ones associated with buying anything second hand. You won't know how it's been treated, any issues it may have had in it's past etc.

Couple of things:
1. Get all the original discs if you can.
2. I would do a clean install of OSX - Whether that be Snow Leopard/Lion/Mountain Lion. This will negate any issues of what's currently installed. Also means you'llset and know all passwords etc.

I have a 2008 Imac with ML, no problems