I posted a answer today on this topic but the site went down and my post disappeared.
Most older lenses are great value and can be as good as the lastest or sometimes even better. I brought a 400mm F2.8 AIS lens for £2,400 which cost £9,600 when new, and it's a cracker regarded as better than the lastest version. The only downside is it weighs 6kg and hasn't go VR. Just check on the web for any infomation about any lenses you want before buying.
