Pay drug buyers to narc on sellers (especially via recordings). Catch the sellers of addictive drugs (especially P/meth) and bust the network by making it too risky to sell hard drugs. However would need a way to prevent buyers from becoming victims of retribution.
If the homeless problem is predominantly due to drug usage then we need an effective way remove the drugs from society. Might help reduce theft too?
Note I am not a fan of persecution for drug usage! Personally, I would prefer to see many drugs (mushrooms, weed, ecstacy) decriminalised and made safe. Currently street drugs are unreliable quality (due to manufacturing adulterants, mixing in fentanyl/crap). I have known some reasonably functional/social users of some class A drugs - so I am not religiously against drugs - but I have also witnessed damage to individuals and society due to drug usage.