Negotiating for purchase a Used Cellphone,..what minor flaws acceptable ?

[RJSV]

    The local shop has repaired CELLPHONEs, as well as a smattering of laptops for sale.
   As a person in 'poor' income situation, I've grown to accept some disparities.   I think my personal income is down around 1/9th of what has been considered acceptable, (for a typical small family).
   I'm prepared to buy a used cellphone, maybe even a phone that has a minor crack, in back of case, or similar.   That's a good incentive for a small shop owner, (I figure), as they most often see finicky shoppers, that don't want to 'accept' cosmetic type flaws.

   A drop-resilient case might be good, as well.   The phones on display for sale include IPHONE15 which could be a nice change.

   Any comments, on helping me make a good phone switch ?   My current phone suffers from touch-screen partial fail....top of screen does not detect my finger presses.