If you are trying to refresh your old blog post, a small minor change of one word is considered a big update for Google Search Engine. So go ahead and update your old blog post as much as possible. All you need to do is read through your old blog posts and change anything if you see fits. Sometimes it might just a small grammar mistake of adding an S but it is consider a big update for Google Search Engine. But if you are trying to update an old blog post of more than a year, I’m sure you will find a lot more things to correct and more content to add.
You can even change the content if you found that the info is out of date. Sometimes in between you might even change your mind about the money making opportunities that you trusted before. Don’t worry about having a different opinion after some time. The important thing is that we need to change in order to survive. So just go ahead if you are changing your content from YES to NO. You can provide a reason when you are updating your content. Money making opportunities that are working yesterday might not be working today. So it is alright to turn around when things changes.