Is there a safe steroid I could use to gain muscle mass. If so what could be side effects? And where could they be obtained?

Depends on your age. Jeffry s life, M.D. Would disagree with the the previous answers. I would suggest reading "the life plan" and googling "cenegenics." if your total and especially free testosterone are below normal levels, either due to aging or disease, you are a candidate for fda approved testosterone replacement, via transdermal or injectable routes. This therapy can change your life, and you need to ask your dr.
NO. Using Anabolic steroids to build muscle mass has been proven to be unsafe time and again. The side effects are myriad and none of them are good. Don't do it, just work out hard and honest and you be miles ahead in the long run over juicing.