What to do with irrelevant pages?

I have a website related to term life insurance . Before I found my niche, the site was about other kinds of insurance and was, frankly, all over the board. I have a feeling that I should narrow the focus of the site by getting rid of some of the old pages, but I'm not sure exactly how to go about doing this. Do you have to somehow set up redirects? If I'm no longer interested in those pages, would it hurt to just delete them?

It wont hurt to delete them. keep in mind that it could take 3-4 months before all your pages are deleted from search engines so it will be a good idea to setup redirection to some of your new pages.

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If your pages are about insurance (all be it other types) I would just leave them there and drop some AdSense on them.

You can remove them from your main navigation so they don't form part of your functional site. If they get some traffic you will earn some money.

If the pages donot show up as landing pages in google analytics ever and if they have no external links pointing at them then there is no harm getting rid of them and no need to do a redirect IMO. If these pages are not relevant to your site now I personally would ditch them (providng the above two things are not happening).