you need at LEAST 6 months of operating costs in a bank account before the doors even open. thats costs AFTER you have stocked your store. 85% of all business fail in the first year due simply to the lack of operating expense money, this includes payroll, rent, tax, advertising, utilities, insurance etc.
ideally you want a year of operating expense money most businesses dont make any profit in the first year. one year of expense money typically allows 2 years of operating at a slight loss until you get the hang of it and name recognition occurs.
the area that is almost always underfunded is advertising. if no one knows your business exists how are you going to make money.
just my 2 primers worth.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith