A rent officer will come round to your house to determine if it is a fair price. You may not get the full amount, but it won't be a huge quantity out, say 20 pounds short, they calculate what they think you should be paying for the property you are in.
Income support will be around 90 pounds a week.
You will still recieve child benefit, not sure of the amount,( someone could post how much they get with one child).
You don't have to pay council tax.
You don't have to pay for dentistry
You don't have to pay for study (which i fully recommend to get you off income support, it does your self esteem no good whatsoever)
Also i would set all your bills to weekly payments, you will be living off nothing and a 100 pound bill would stop you eating for a week. Get everything you pay for into small amounts.
Anything else you want to know just ask, especially about cheap shopping