The answer could be "Yes" and "No". In some cases, yes you should buy the expired domains but it will be opposite for some other cases.
Yes you can make money using Expired domains.
- You can find Expired domains with high metrics and can sell the domains on Flippa
- You can find expired brand domains and then contact back the brand owner to get back their domain in slightly high price.
- You can find expired domains with high DA, PA and TF and sell guest posts on those domains. Fiverr is a good option to sell guest posts
- You can create a professional website on your expired domain and then sell it in high price by getting a few daily members with little SEO.
But you should be very careful while finding and buying expired domains. You should check it is not penalized by Google and at least it has 1 page that is still indexed in Google. you can it using this query in Google.com ==> site:yourdomain.com
You can watch this video to learn how to find high metrics expired domains to earn money online.