A human can go for more than three weeks without food (Mahatma Gandhi survived 21 days of complete starvation), but water is a different story. At least 60% of the adult body is made of it and every living cell in the body needs it to keep functioning.
You cannot raise the rent if you and the tenant have agreed, usually in a written lease, on a certain amount. Usually, you and the tenant will agree on a certain amount for a specific period of time. Once that time period ends, you can raise your rent with 30 (thirty) days written notice. If you and the tenant never agreed on a specific period of time, you can usually raise the rent with 30 (thirty) days written notice.
If the tenant is behind in the rent and has an oral lease with the landlord, the landlord needs to give only fifteen (15) days notice between April 1st and September 1st, but thirty (30) days notice between September 1st and April 1st.