How long does a ich treatment last

Hi , someone whats to give me a fish but it has ich. He's treating it, but i'm less that enthusiatic about taking a fish that has that problem. How long does this treatment last usually.



Its an adult yellow wrasse



I have a few questions as well;



- If he survive is he a carrier

- Should i QT that fish again before adding it to my tank

- Should i take him at all.

- Any other precautions or stuff i should know thanks.