I started from scratch but had to buy the lease to get the tenant out. I think the whole exercise has cost me circa 25k. You will need alot more then you think as a contingency as rent has a habit of sneaking up and biting you on the bum when you start out!!

It really is difficult to say what it will cost you, depends on location, state of shop, what you intend to do to it, stock, etc etc. Like someone else said, think of a figure and double it. Also dont expect to earn anything for quite some time.