Let me guess. You acquired your knowledge from TV and Sunday School lessons. I remember the scenario. A "pusher" gives an innocent victim a free sample (or a shot while sleeping) and the victim is "hooked" for life, right?
Sadly no, people I love dearly.
I didn't used to believe that a pusher would give free drugs --- until I met quite a few people who actually did have drugs put into their drinks or offered to them. A lot of cocaine addicts didn't have to pay anything for their first couple of doses.