There is great complexity in helping homeless people in all their diversity. I was called out as cynical in another thread of social projects, so I will try to be more clear here.
Social projects like this one have just as much risk as a regular startup. Most will fail, just as most startups will. But this is no reason not to start a social project, just like with startups.
I have the impression that people have two reactions when reading stories like these: i) people love the idea and that someone made it happen, and are glad that it exists, regardless if it will actually impact a lot of people or not and ii) people think it will fail, normally for obvious reasons and that the project shouldn't have started at all. It is a waste of people's time, money, trust and will.
Myself, I pretty much act the same way as with any other Show HN for a regular startup. If I love the idea and I am impressed by the execution and potential, I just share that and go on to sign-up or buy the product and share with my friends. If I see flaws, according to my own view, in the idea or execution or vision, I go on and comment, trying to help. If I don't like the idea or the vision, I just ignore.
So I'm commenting here because I liked very much the idea and the vision. But helping homeless is a tricky business. A little bit of counterintuitive, but homelessness is less correlated to previous poverty compared to other social issues. I lack some studies to cite here, this is personal experience working with homeless people and talking to people with more knowledge on the subject than me (in Brazil and Uruguay, but one of things I learned is that homeless people have a lot in common all over the world). Maybe HN may attract more qualified people on the subject than me, but I do have some practical experience with it.
Poverty does not cause homelessness. There is a diversity on homeless people in relation to their social status and wealth. What makes someone homeless is lack of social networks, not money. Social network as the people you know, not the websites. You become isolated, unable to ask or receive help from close family, far relatives, friends, colleagues, acquaintances. The reasons you lost all your human support has much less diversity: alcohol or drug addictions and mental illness are the most common. Also common is just geographical separation, as with migrants. There is a shame in going to the big city and "not making it".
That big, maybe dispensable intro, was to say that you must provide the structure, just as "Lava Mae" did (very well by the way, as being mobile it is a great solution). But also you need incentive (which I honestly don't know how Lava Mae provide). Just as in tech, if you build, you don't know if they will come. There is a lot of reasons a homeless person might not want to get in the bus. They don't trust the people there, they just don't want to have any contact what so ever with another person, they may be afraid of it, they may consider their dirt an important part of their persona, they may be afraid of loosing their stuff while bathing. I see that they have the purpose of being "a safe and welcoming environment". But that may not be enough.
Not paying enough attention to incentive, marketing and distribution in this kind of project is dangerous. To build something and complain that no one comes is just as silly as in the startup world. But in this case you still cause more harm because a lot of people might look at it and come to the conclusion that we should quit helping homeless people, after all "there was that bus to clean them and they didn't want to get clean. Everything was there, it was their fault".
So I want to end this comment with a sugestion. Here in Brazil we have some government restaurants that charge R$ 1.00 (~U$0.40) per meal. Enough that anyone can afford, even the homeless (if I recall correctly, even the R$1.00 fee is optional). The food is good enough, I ate at one several times, and the restaurant of choice of a lot of lower class, employed people. That provides dignity to the place. And it is very clean. It is open for everyone. So when a anyone come to eat there, there is just one discrimination: you must be clean. And the place provides a bathroom for the homeless people that need, to take a bath, be clean and then eat.
The magic is that at once, you provide a good incentive (to eat), with several good explanations of why should the homeless person get clean at all. It is not because people in the street will avoid you, or that you will annoy society. It is because eating is a special circumstance, an important ritual and place. People will be sitting close to you and they have the right to eat without getting dirty and without smelling bad. You will eat on a proper place, with proper tools, and then you must be on proper shape to eat. Among with other assurances such as that their stuff will be safe and untouched when they finish.
This could be a "growth hack" to Lava Mae (IF they didn't think about it yet, which I just don't know). Pair up with some restaurants, soup lines, or whatever food service for the poor they have in SF; ask them to require the people to be clean to eat there and Lava Mae provide the structure.