José.
You are absolutely right about Housing, transportation and food (in that order). If a person could elimate any one of these, they would have tons of money. THe rest amounts to nothing. If you didn't have to live in a shelter, you could have 50% of your income for discretionary use. (Gear )
I ride my bike 11.5km to work and 11.5 from work, if it's nice out. This saves $4.00cdn/day and reduces my blood glucose. I almost never eat out and only buy inexpensive foods. I could live on $20.00/week if I could eat more carbs. RIce and beans is really cheap.
Starkeeper