Like another said it's impossible to give a range because it all depends on what you're going for with your business' focus and how new you want your equipment to be. At the minimum you're going to need to research the requirements for both your local, county, and state. That's going to dictate pretty much 98% of what you do to the space. On the low end, it can be a $30,000 investment, or it can go into the millions depending on what you're going for with the space.
For me, I'm building a building on the property which we live and because of the size of operation I am I will be allowed to connect in to our septic as it is. I've also been purchasing SMART for all of my equipment and supplies with the main focus being on not going into debt to own it.
The other thing is you really NEED to create a real world business plan. Not the frilly ones they have with the SBA or a university course, things like licenses, inspections, staffing situations (the more staff you add the more responsibility YOU have), insurance, what it REALLY costs for a hood/ansil system with installation, what it REALLY costs for the commercial floor, what it REALLY costs for staff, electricity, paper towels, toilet paper, and how many cakes you realistically need to sell in a month to pay all of those expenses plus when times are good saving that money to pay for the lean months. You can't tell people "I'll pay you next month", you've got to have money on hand to survive 5-10 years without making a dime yourself. You've also got to include what the costs are going to be to your relationships. With a storefront you can't just take the weekend off, you've got to have someone working and if they call in sick, you're SOL on your vacation you planned for 6mo. Same goes for what happens when your kids get sick and you've got cake orders up the wazoo.
This is why I had my kitchen set up as a "made to order" operation. I can plan to take a weekend off and I can control EVERYTHING how I want it to be. I don't have to take an order if I don't want to. You've got to really consider what you're willing to pay. You've also got to have your time management mastered along with an area set up for efficiency. The other major thing to remember is this is a BUSINESS, it's not "for fun", The only reason to be in business is to MAKE MONEY. Your drive is what will get you up in the morning after working for three days non-stop to deliver the cake on time.