David Casarez came west to Silicon Valley with his life in a van and startup dreams in his eyes. Within months, the web developer and would-be entrepreneur was hugging Apple CEO Tim Cook and interviewing at the legendary tech firm. 

But no job offer came, from Apple or any other company, and Casarez found himself sleeping in stairwells and on park benches, surviving on pouches of tuna and ramen-noodle cups, twitching at every night-time noise and weeping over his plight, he says.