All good points. You can keep your options open by working on your venture, which makes an excellent 'story' for a top 10 application, and also acing the entrance exam which is good for 5 years. If your business ends up taking off the you're only out the money for registration and effort spent studying, and if not you will have some hard earned experience compared to your B-school classmates.
I don't know how schools look at age, so you'll have to make that decision at some point but probably not now.
I don't know how schools look at age, so you'll have to make that decision at some point but probably not now.