If it's anything like the UK then be prepared for a shock.
There are differing amounts of data that can be licensed from companies, but if you want more than simple data then you should be thinking big numbers.
It's not unusual to see 6 figure sums quoted for very good data (and many fields you won't see publically) on 2 million UK businesses. As for how you can use the data, you have to make sure you are allowed to use it in the way you want.
There are ways to get business data for free (even in the UK), but you won't have anything new to offer your users. I'd have to be very certain of where your revenue is going to come from before investing heavily in becoming a competitor to the IYP's.