Strictly speaking with a restaurant your largest expense, rent, is ongoing rather than upfront. Your point in general is valid, though I would argue that for someone truly motivated to make a point, it's not impossible to start with smaller businesses (incl. non-software businesses) or a bunch of savings and progressively work your way up to kick-starting larger business.
Some require actual buildings, expensive equipment, etc before they can even exist. A restaurant is a case in point.