Do you ever try to find a second home for a story you have written and had published? The term we use is reprints and it can bring in a little more cash if you adhere to a few guidelines.
Consider these when thinking about selling reprints:
What is considered a reprint and what isn't? If you want to sell the article/story again exactly as you originally wrote it, then it is a reprint. However, if you make substantial changes, then you have a new article to sell.
What about rights? This is one of the most important considerations in reselling your work. Always check to see what rights were purchased the first time the article was published. Some publishers buy first rights but also stipulate the article cannot be sold again for X period of time. If you signed a contract that gives the publisher all rights, then you can never sell it again. Most writing guides will discourage a writer from ever selling all rights. I did it once early in my writing life and I've regretted it ever since. Some publishers will buy only electronic rights. In that case, you can sell a second time to a print publisher. Whatever the case may be, the rights you have sold are extremely important. Save yourself a lot of grief later by checking first.
Where can I sell reprints? Surprisingly, there are publications that actively seek reprints. They don't mind being the second one to publish your work and they are happy that they can offer you less money than the first publisher did. You've done the boatload of work the first time around so less cash the second time is probably alright.
Use your favorite search engine to find markets for reprints. What this requires from you is time to do the research, time to prepare and submit and time to wait for a response. I don't see that as a problem because, if we want to sell our work in any form, we have to invest some time in finding the right place--new or reprint--it does not matter.
Is there anything else I can do with an already published article/story? Yes, you can rewrite it using a different viewpoint, a new argument to a problem or inserting new information that will change the entire piece. If you do that, you have two benefits: 1. You already have the bones of the article/story and 2. You can sell it as new rather than a reprint.