I got approached from a local business/corporation about using a pic of mine, all in all this was the question.

Would you “sell” the rights to use this to 4Life? And if so, how much? Not sure if it will be a one-time usage or more. Let me know

It would be used for their magazine publication. What would you charge for something like this? I don't have the first clue. I know there is a book out there with usage fee qoutes. Any help on this would be appreciated.

Depends on the company and the magazine. If it's a mediocre local zine, then you'd be lucky to get $500 for a cover image, regardless of what pricing guides say.

As for the rights, what are the chances they would actually use this again in any meaningful way?

And do you like the image enough to retain the right to sell it to someone else in the future (nonexclusive for them)?

One way you can get an idea of pricing is to go to one of the big stock photo sites, find an image similar to yours and check out the pricing for that usage. Like Corbis.com.