The 15 hours childcare, for those whose children are old enough to get it, leaves you much less than 16 hours to work- unless you can get 15 hours a week in the same nursery, then you need to allow for travel from nursery to job, and find a job whose hours match those the nursery offers.
If you are paying £500 pcm into a mortgage, you will eventually get richer. If you are paying rent, you never will.
If you or your child have a disability, it will cost more to live.
If you are poor, you will make worse decisions and choices (research shows the stress of poverty negatively impacts people's IQ) and get even poorer.
If you have to move to cheaper housing, you lose the support network that keeps you covered if children or you get ill.
If you are poor, your bills cost more because you are put on higher tariffs (pay as you go) and need more fuel to keep your property at a passable temperature.
Work in a food bank for a week, then tell me it's a good plan.