Advice on data capture business - please!

[nk400]

Bit of a different business to the usual but here it goes:

Been toying with the idea of launching a business designed to capture marketing data. I know how to capture the data (legally of course) but I only have very vague ideas about the rest of my plans.

Does anyone have experience / knowledge of selling data etc to businesses? It would be in the form of detailed or more generic consumer opt-in data (not email address), data which can be highly targetted & bespoke if neccessary (i.e a sort of 'focus group') created if needed.

Simply I need to know how to monetise this side of it. I do know it can be done, but unfortunately not how!

Any advice appreciated.