Think about it from the other point of view - the hiring manager has 20 people in front of them who can do the job. You need to tell them a story that shows it is better for that manager to hire you vs. the other 19. You being homeless and not having steady work for the last three years is a big negative (perhaps unfair, but true), so you need to not just show you can code, but show that you have better work ethics, can be more productive, or something else that puts you above and beyond the other 19 guys.
Admittedly, that will be tough. So if you aren't able to do that, then you need to build up a history of good, recent work. Take advantage of being homeless, and offer your services to local non-profits who work with the homeless. They almost all need some tech help, even just to organize and report on their data. Helping out will build up a track record of getting things done, and a network of people who can give you references for your capabilities, as well as let you know who else need help. It is possible that starting a small consulting service doing such things is easier than landing a full-time coding gig.
Admittedly, that will be tough. So if you aren't able to do that, then you need to build up a history of good, recent work. Take advantage of being homeless, and offer your services to local non-profits who work with the homeless. They almost all need some tech help, even just to organize and report on their data. Helping out will build up a track record of getting things done, and a network of people who can give you references for your capabilities, as well as let you know who else need help. It is possible that starting a small consulting service doing such things is easier than landing a full-time coding gig.