Im thinking to start a business for web and data analytics.?

[Jake]

Sounds highly risky, I would say you would need to partner with someone with internet business and marketing skills, who has worked in a field that employs analytics.

There are various online data services, some which have scoured the web to crate their database provided for a monthly fee.

You can find several example advertising spy services that monitor banner ads impressions on the web, if your specialty was coding web apps and databases this might be a field to get into.

One example service that seems to have compiled a comprehensive database of ads and companies on various ad networks is:
Adbeat.com they offer a trial period you could use to get familiar with their operation. Typically internet marketers waste a lot of money testing various ad designs and placements to determine winning combinations, modeling others' successes can shorten the path to success.

other spy tools
spyfu
LotsofAds
AdZeta
SpyNinja
WhatRunsWhere
BoxofAds
Blackpops