(This post is really about lenses for all camera formats, including MF and 35mm. I just posted it here because this forum seems to have the most activity.)
I keep hearing about the occasional lens being destroyed by fungus. When I'm browsing on eBay for lenses, I see that many sellers point out that their lenses have no fungus. But I've never seen an example of what a lens with fungus looks like, or what it does to your image.
I'll go ahead and assume that fungus is the death knell for any lens. Given that I'm pretty young and am investing in some quality camera equipment, I want to make sure that none of my lenses succumb to fungus. What precautions, if any, should I take?