Haze is usually when, over time, the lubricant in the lens has atomized (fumes) and leaves a film on the inner elements. If it were me, I would avoid that lens... unless you plan to take it apart and clean it. I collect vintage lenses. Sometimes haze can interfere with the image. Dust isn't a huge problem. Haze can be. Just my 2 cents.
When you get an old lens that has been advertised as no fungus or haze be sure to shine a bright light through it when you get it to make sure it isn't there. Fungus can be a huge problem as it will sometimes etch the glass. Haze doesn't always clean up either. Personally, I would not buy anything that admits to fungus or haze.
Be patient in your search. You'll pay more money for a good lens, but it is worth it.