No, you do not have to submit proof of your income when you apply for a residence permit orientation year. You will have to sustain yourself during the orientation year, but you do not have to show how. You will be allowed to work during your orientation year.
During the orientation year you are not allowed to use public funds, like a social assistance benefit. Receiving, for example, an unemployment benefit (in Dutch: WW-uitkering), a sickness benefit, rent benefit, healthcare benefit, childcare benefit and/or supplementary child benefit is allowed.