My impression is you wouldn't have been able to guess that he was homeless X years ago based solely on his middle-class life now. Real bootstrapping
I believe one of everyone's worst fears is to be homeless (whether acknowledged or not - I hate inevitably thinking about it whenever I see someone on the street).
The good thing though was that it made me feel like I could cope with anything. Homelessness reduces your horizons to "where am I going to sleep" and "how am I going to get some food" (to the point were those two things are all you think about most of the time) and having come through that I felt like I could try anything because no matter how badly it went wrong I would be ok.
The only part of this I've personally experienced is similar chicken and egg problems trying to move to new country. You can't get a apartment without an employment pass, the bureaucracy can't send you letters without an address. If you have money you can bootstrap off a lawyer or accountant's credentials otherwise there isn't always a way.
You have to experience a problem to know how to solve it; and the problem isn't always as serious as being homeless. 37signals built their own Project Management platform, for example.