I can't tell you whether to go get an MBA or not or start a business now. Personally I believe that working for a few years and then getting my MBA helped me immensely in starting my business, but I also feel like if I had worked for a few years and then gotten my BBA that I would have derived much of the same benefit. The degrees have so much overlap that it's almost a waste of time unless you plan to use the MBA to go to a high powered corporate career. I can tell you personally since I was a kid I always started little businesses and wanted to have my own, but after my MBA I thought hey I can be the CFO of a big company someday - they get paid a shit load and I spent all this time in school, why not? So after MBA I worked for 2 years got 3 promotions then got laid off when housing crashed. So it didn't work out for me and I was kind of forced into the entrepreneur path I always wanted by virtue of no great job prospects really being around in '09.
A little advice from my experience. The business will take longer to start than you think, and it will cost more than you think, in almost all aspects. However, if you already have one location you know a lot of the unanticipated costs that pop up. You are talking about the business:
1) Supporting both you, and your partner's living expenses I assume? and
2) Over and above that generating enough income to open a new location.
Even if you guys are going to live on savings and put all the company's profits into new locations, just remember to consider your run rate on your personal savings, your personal mental threshold on how low you can allow that to go without puking, etc.
Make sure you have enough money, or as I call it, "staying power" to get you through that time.
Don't spend money on anything you don't absolutely need. If it isn't literally, directly helping you sell your product now, don't buy it.
I'm not sure if you were an independent contractor when you were in the mortgage business so you might already know a lot of stuff below, but I didn't. Please don't be offended if you already know it I don't mean any harm.
Make sure from Day 1 you have a system for keeping track of all your accounting shit. I was careless with that for the first year and I had to spend about 3 weeks of wasted, useless useless time assembling it all at the end of the year because I didn't have a system for organizing receipts, tracking expenses etc. Not only that it became a source of anxiety for me because I knew I wasn't on top of that portion of my business and it consumed valuable mental energy. And this was after I had my MBA. I was so focused on growing that I fell into that stupid inexperienced entrepreneur trap. For business receipts I have found a smartphone camera combined with Evernote is a life saver. As soon as I get handed a receipt or invoice I snap a high res picture of it, label it on my phone, tag it and 1 button hit Upload to Evernote and it's done and organized for the CPA at the end of the year. For tracking income/expenses there are lots of systems.
Taxes are HIGH for small business owners. You will pay not only your usual tax rate but also 15.2% on your first $100,000 of income for Medicare and Social Security, far more than an employee pays. You do get to deduct a lot, but just realize that and put them aside every month without fail.
You don't pay taxes once/year when you are self-employed. You have to pay quarterly estimates to the IRS. If you don't they penalize you. I learned that too.
I don't know what your business is so I can't tell you much else, but in general those are some real world observations. All I've ever heard people say is that food is tough, tough tough. But most people say all businesses are too hard to start, already been done, etc., and look at all the restaurants/new foods out there. If it's a food store or restaurant make sure you factor in the cost of a GOOD manager to take over when you guys go to start new locations, not some monkey. The extra money to get someone competent to be responsible and a good steward while you aren't around will be worth it. And still put cameras everywhere anyway

trust is one thing but your business is another.
Of course do your GMAT!
Oh yeah also it will be the most fun, exhilarating and stressful thing you've ever done in your life. Once you do become established it's a feeling of accomplishment like you could never imagine. And I always thought people were full of BS when they said it wasn't about being wealthy, it was about time and freedom to do what you want with your time, I said BS I want to be RICH. but now I realize the wisdom of those words. I'm not saying I'm wealthy but I can do what I want with my time. And I don't play golf so whenever I want to I can just sit on my couch with Lawrence and do two chicks at the same time.