This is a subject which comes up, not too frequently, but with some regularity.
My first inclination was to dismiss this as a joke, Obviously I was wrong to do so. The fact that the idea reappears, often in a post that is seemingly quite serious, leads me to believe that that the question is serious.
It is not beyond belief that there are people who feel such desperation that they are willing to attempt such a procedure. Others, thinking that the cost of surgery is beyond them may resort to such an attempt in the hope that having started, they would then qualify for emergency intervention to properly complete the procedure.
If such were the case, the individual would be in for a rather sad awakening. About the best you could hope for would be a trip to the Emergency Room where your wounds would be closed by someone with minimal skills. Scars and disfigurement would be the most obvious outcome. Trying to maintain a sterile field would be nearly impossible so infection would be a common result.
Years ago, I was in the USAF. Not a medical professional, I was a Medical Corpsman and for several years I served as the chief Medical Tech. in a Hospital Emergency Room. Based upon my experience, I would say that no one actually qualified to perform such a procedure would attempt it on themselves. The Doctors that I held in highest regard would not even treat members of their immediate families.
One of the things a Doctor needs is the ability to be totally objective. I do not believe it is possible to have the necessary objectivity when dealing with yourself or with someone with whom you are emotionally involved.
The procedure of male breast reduction is not difficult to describe, but it requires the skills of a surgeon coupled with artistry of a sculptor. This is definitely a job for a professional and not a Do-it-yourself job.