Lens fungus

I would steer clear of any lens that has fungus unless you intend to have the lens professionally cleaned, or clean it yourself. No idea what the difference is between "light" or "hazy". Perhaps just a matter of degree. Some fungus can actually etch into the glass coatings.

If the price is cheap enough it may be worth a punt.

quick answer..yes keep away
plenty of decent lenses out there

Just to add to this, I did actually acquire last year a Pentax A 16mm 2.8 fisheye with fungus. It is quite a rare lens. I bought it as part of a job lot and it's net cost to me was next to nothing. The fungus cleaned up nicely everywhere (it was worse in the dial-in filters), except for a small patch that was growing behind the front element in the centre. The technician who cleaned it for me was not able to get direct access to it so despite best efforts there is a small patch still visible.

So even if you pick up a cheap lens there is no guarantee you will be able to clean all the fungus off.

ps. there is a M 40/2.8 on ebay at the moment that comes complete with an insect inside !

if you want a longer lens then go for a da 55-300 its a great lens

and quite a few come on here for sale at good prices