I think living with your parents is equivalent to earning AT LEAST another £17k (Assuming you're a basic rate tax payer, who pays national insurance contributions and contributes a small amount towards a pension scheme)
Monthly costs:
Rent/Mortgage: ~£450/~£600 (£600 based on a 25 year mortgage of £130k, less than half the national average price, at low interest rates)
Council tax: £80 (About average for a property in the £130k region, with a working occupant who gets the 25% discount)
Electricity and Gas: £60 (Probably less than most people would use if anything, especially in cold months)
TV licence: £12
Phone and Broadband: £18 line rental + £17 for call and internet package = £35
Home insurance: £25 ( Bank would certainly insist on building insurance)
Water: £25
Maintenance: £50 (Covering appliances and fixtures and fittings)
Total: £887 a month
How much you'd need to earn a year working full time on the minimum wage to have £887 a month after tax: £17000, meaning you'd need to earn £32k a year.
I think I have been very conservative if anything and underestimated. The £130k house price was factored in for a first time buyer, a more expensive mortgage would mean higher repayments obviously. £50 a month may cover maintenance, barely, but I also haven't factored in the cost of new equipment, appliances and furnishings (TVs, fridges, beds, DIY) these tend to be paid off over a period of time or saved up for, monthly, so in reality this would be in the low hundreds a month. Economies of scale can be made by buying as a couple, but couples tend to buy larger homes meaning higher mortgage payments, higher utility costs etc. so the cost is by no means halved.
Of course many people contribute towards living with their parents/family when they're working especially as they get older, but nowhere near £900 a month. I also haven't factored in food costs, as some people still eat their parents food or benefit from the economies by buying together, so this could save them £100 a month at least.
Do people agree with my costings?