If you want a simple business model that works, sell t-shirts on a high pedestrian traffic area or tourist trap area (pier 39 sf). You may even clean people's car windows for tips and pay at gas stations if you ask the owner|manager & explain (many gas stations are independently owned.. Expect to have to visit 10-15 stations to get approval and be super sincere). It's generic hard work, but it's doable without skill or funding. Also sign up for TaskRabbit for more skilled jobs that could pay more. (See a pattern.. Try lots of things and hustle to get to higher paying gigs.). Btw playing up youth leads to money... Stay clean, shave, youthful attire and get a haircut if needed... You're the product if you offer a service. (Either look professional or super pathetic, in between leads to less cash.)
Some religious organizations will help you, others like most of those in Silicon Valley, only do happy-clappy and no social service volunteering as do others in poorer areas. In fact if you ever had to bet outright, don't bother begging from rich people, beg from lower/middle class areas.
If it's a super emergency in the US, apply for food stamps and general assistance at your local social services agency. They'll usually give it to you the same day in the form of an EBT card that works at Costco, grocery stores and pharmacies. It's a pittance, but it will keep you alive if you budget it very carefully. (Beware: massive fees at almost every ATM. Always get cash back at stores instead.) They may even throw in medical insurance if you're broke enough. (I was a teacher in a minority area and had to help emancipated students get food and get to school... I've seen almost everything. :( ). Rationalize going on the dole as a buffer that you will pay back through taxes many times over later, or to wealth and minimal taxes and let the middle class handle that.
Cut your expenses (don't eat out) and travel as least as possible. Maybe buy a cheapish van and live in it instead of paying rent. Cancel all those monthly Internet services (games, Netflix, Hulu, spotify), perhaps even phone service. Use coffee shops for power and data, maybe go Skype / google voice only. Cut luxury prepared foods too. Shelter, food and transportation (gas) are the actual necessities... Everthing else is a choice to rationalize excessive consumerism. (Stop smoking, drinking and latte habits if present... This is where most poor people hemorrhage money and may harm their health too. For blanks sake don't drink or do drugs but do get good sleep, your judgement (wits) needs to be perfect or one mistake on the street will kill you... You need to be making the best possible decisions as often as possible to bootstrap yourself back to where you want to be.)
Don't count on a startup for income... It's always a long shot / crapshoot and most stories are pure survivor bias hiding the work, pain and luck involved.