Sleep training at 4 months, thoughts?

Been cosleeping but we're exhausted and considering sleep training. Read some articles and got conflicting info. Some say it's fine at 4 months, others say wait till 6. Wife is leaning toward trying it, I'm nervous we'll traumatize him but also I haven't slept more than 2 hours straight in months and I'm losing it. What did you guys do? Are there ways to do this that don't feel cruel?