Originally posted by hjoseph7 Does the M-series lenses have a focusing AID that will help you focus with a DSLR such as the K-5II ?
Focusing aids would be on the camera, not the lens. So, no.
Just like 50mm lenses, there are not many bad 135mm lenses. Though older ones will not have the better coatings. For example the Takumar Bayonet 135 f/2.5 is a very sharp, very tiny lens with built in hood that gets little love because it has relatively poor coatings and flares and loses contrast when pointed anywhere near the sun. But used properly it produces great images.
Whether you need AF or not is up to you. I've used manual focus 135mm lenses and they are not bad, I've used AF 135mm lenses as well and I'm not going to go back to manual focus. The Pentax F 135mm f/2.8 is one of the best and my current 135mm when I can pry it out of my wife's hands. I also have the Pentax A 135mm f/2.8 and it is also a joy to use and gives good results.
But you do not give enough details in your post to give good suggestions. A "135mm f/3.5 on ebay for 50 bucks" can mean just about anything. There are probably 25 different lenses that description would fit.