Try posting this in the new retail section.
I 100% disagree with buying a business, you'll be paying heavily for someone else's "vision" and probably just want to change 70% of it all when you move in anyway.
Cost - roughly:-
500sq ft retail area (as an example)
Insurance inc public liability, £1k cash left in shop overnight, basic contents (i.e tills, credit card machine, £30k stock, £20k fittings) £250 -£300 pa. Buildings obviously vary vastly but approx £300, doubt they are included in a £50 lease.
Credit card machine - join the FSB for £100 pa then you'll pay £15 a month rental instead of £28 (about!) and get a cheaper %, plus have the benefits of free legal advice etc (not that I've ever used any of their other services!)
Legal fee's approx £1,500
Shopfitting - anything really, but laminate flooring about £2k.
Signs - again variable but approx £700 for a alli' 8ft x 2ft
Rates - check these carefully, at £50 a week you rates will probably be more than this.
Stock/product cost - only you will know this
Advertising - essential to run regular campaign for a minimum of three months so people know you are there, and then remember you are there. Don't skimp on this. Cost - check with you preferred provider, but a weekly ad 3 columns x 10 cm's in a local rag will probably cost about £90 a week.
VAT - kicks in at about £70k mark.
Most important - DO NOT expect to take any money out of the business for a least three months, best to budget for a year with no income. If you can't manage at least three months don't start the business.
I think that's the basics, and as I said only a very rough guide. Hope it all goes well.