I started with black market, then switched to prescription as soon as I could. And yes, it was testosterone I took, so that is possible to get via black market, although definitely much harder and riskier than estrogen. However I got safe stuff, from other trans guys who sold me their left-overs that they had gotten prescribed.
But the tricky part was regulating my dose, cause I had no means to get my levels checked. And guesstimating that by my feelings and bodily reactions alone wasn't exactly optimal, although I mostly just relied on the recommended dose according to the package and never strayed far from that. I did that for one year, then stopped cause of the health risks I was subjecting myself to, and the mood swings. But then went back on it again a few months just before I got it prescribed.
I only did that cause the gender clinic I went to, which diagnosed me with GID and all, refused to let me start hrt. So I turned to the black market just to survive my ever-increasing and life-threatening dysphoria, while I kept begging to get it prescibed instead. Eventually I did, after 4 years of waiting. I'm still surprised I somehow managed to survive those years, during which I was completely left to my own vices... with a bad mental health state.
As soon as I got it prescribed I ditched my black market hormones and haven't used them ever since. That was around 6 years ago I last took them, and almost 9 years ago I started taking them (years 2010-2013). Then I was on the prescribed version for 5 years (2013-2018). All the starting and stopping of hrt conveniently happened around months August/September, which is neat for the counting.
There's no means of informed consent in my country. You only have to either jump through all the hoops and hope you pass, or go black market. I wasn't so lucky with the hoops.