What is the text of the error message that you are getting ? As long as the email address isn't currently being used as an account's primary email address or alternate Apple id then you should be able to use it on a new account (though it might be best to not use a business email address, or an Apple address i.e. me.com, icloud.com, mac.com, some people have had problems with them).
You can remove alternate email address from an account by logging into it via http://appleid.apple.com, and you can also remove the rescue email address (by answering your security questions on the Password & Security section of that site) - but being an alternate or rescue email address on a different account shouldn't stop you creating a new account with it
Generally it's best to only have one account, all content that you download from the store will remain tied to that account, so only that account can potentially redownload that content, download updates to its apps, and authorise it on a new computer - you could also end up tying a device or computer to an account for 90 days, and not be able to redownload content from a different account until those 90 days have completed : Manage your associated devices in iTunes - Apple Support