My wife is semi-pro, I've helped finance, like every birfday and Christmas etc. She got a 150-600 tamaron to play with this past holiday season...but has a few nice canon lenses as well.

I like to compare local used prices to ebay, like the mark III above is roughly $400 all day, and the mark IV averages to like $900 on ebay.

What is your budget? Its easy to spend $4k on one body and one lense.