This is not a comprehensive solution, but it is - something of a solution, a start, as it were, and addresses a few of the more obvious issues.
Firstly, to observe, it's beyond an "epidemic", the addiction, homelessness, mental health issues that plague central Vancouver and East Hastings districts. It is a full on Zombie-Apocalypse.
The most important thing: Free drugs. Decriminalize drugs. The government can provide these at outlets for those who want them for absolutely free. Heroin, cocaine, most of the common street drugs can be had - without the intervention of the criminal element - for pennies a dose. And by the government providing them we not only reduce the influence of organized crime as well as associated crime by junkies looking to purchase their next fix, but overdoses as well. This is a "Win-Win" no matter how you slice it.
Given the abundance of vacancies in the area - I mean completely vacant, run-down hotels, housing should be provided as well. Both permanent and transitional, for those that want to move on in their lives. Nothing in the least bit fancy, merely a place to get in out of the rain, off of the street, to get cleaned up, showered, store some personal possessions.
For those that still prefer to live on the street lockers can be provided. Lockers, positioned throughout areas with higher rates of homelessness so that they have access to the ownership of property. Property is generally considered an inalienable right. Property, in Western Culture, certainly, defines you. This needs to be addressed, for sure - but it's not the first thing we should be addressing in this regard.
Public Washroom - this should not need explaining. Public washrooms should be made accessible and available on every block - the savings of having accessible toilets - vs the public disgust of stepping over diarrhea, shit, vomit, etc - we've privatized the most basic of needs - dumping the onus on small businesses that for good reason don't want to allow homeless access. "You need to buy a grande latte to take a shit, sorry sir..." - we've commercialized the most basic of human functions. While Vancouver has more public toilets than many major urban centers, clearly it does not yet have enough.
Cash Paying Jobs - working for the city, at a fraction of the rate of contracted or unionized city workers - cleaning graffiti, picking up needles, litter, etc.
Homeless people have a community - and would police themselves. They would quickly put an end to the Graffiti and the littering of needles. They would be invested. At which point they could be put onto more challenging and rewarding projects. Beautification projects. Give them housing in the community. Give them charge of the community. Instead of Graffiti, allow them to do Murals. If they show promise in certain roles hire them on - working for the city or in other roles. You would be surprised at the reservoirs of untapped talent. And drug addiction - on it's own, especially heroin - does not mean you can't hold a job or productive role in society.
Begin enrichment programs. Partner homeless/addicts/mentally ill with sober and healthy people in the community - they need networks of people other than themselves to evolve. Find what motivates or interests them and assist them with becoming involved. Many of these problems stem from a lack of engagement - being invested and engaged is often the first step on the ladder out.
Remove the Stigma.
Addiction, Homelessness and Mental Illness - are SOCIAL Illnesses. They exist generally in and as a result of Society. In the instance of Native Peoples - who are over represented in every instance - it's a response to generational trauma - to being displaced from their lands, their reserves, to having their children taken from them - or being the children that were taken. For the rest, there are probably as many specific circumstances as there are homeless. But - they should not be blamed, they should be assisted in making better choices, when ready.
Ignoring these issues costs us far, far more than addressing them. This area, that we allow this, without assistance or intervention, it marks us as a third world country. We should be embarrassed. We can do better.