I would have to agree with most posters here, get older glass, consider adding a cheap filter in front, specifically anything rebranded by a camera store seem from my experience to be the worst. Canon and nikon branded filters are also pretty bad, Hoya are pretty good, and SMC Pentax are the best (in my opinion, after doing a simple test using my Super tak 85/1.9 and filters from all these manufacturers, while shooting into a low voltage halogen track light in my kitchen)
Avoid any lens that says MC implying someone's version of multi coating, or SMC if getting pentax lenses, as they have some of the best coatings available,
Not using a hood will add flare if it is in the field of view or just at the corner, and also reduce contrast.
You can also get great faded out circles on you lens from reflections if you put shinny bits behind the lens so that you tget sensor reflection
I had a lens like this once, but fixed it with some balck paint. perhaps if you want ti, I can un fix it