Drugs are trivial to get, for the most part.
Theft is obvious, and you can buy most of the well known ones on the street. You can save up prescribed meds.
If I wanted something like valium, as a loose example, I could have a bottle of thirty in about two hours. Opiates would be similarly fast. The more obscure the drug, the harder it is, and the less recreational value it has, the harder it is. Addictive drugs can actually be a little harder compared to the stuff that isn't just because it's market dependent. If the demand is high enough, finding a dealer that has the drug of choice in hand is harder.
This is why I keep all my meds locked up, regardless of their recreational value. Desperate people just grab everything and go. Not just suicidal people, but addicts, folks in pain that can't access healthcare, or just stupid kids looking to self medicate. That's also one reason I don't let strangers in the house, and nobody at all unsupervised, other than two friends that would kill themselves before stealing from a friend.
Hell, I'm kinda surprised you don't already know people that can/would get you drugs. There's usually a black market around hospitals and other medical facilities, and it isn't difficult to find them.