The backlink profile of a recently-available domain is a double-edged sword. While some expired domains have been well cared for by their previous owners and have high-quality links from reputable websites, some contain quite questionable backlinks. The worst case scenario is that the domain was merely used as a link farm to strengthen a major project in a satellite domain network and has already been penalized by some search engines.
Park the domain with a domain parking service. Since you may not have content to put on the site, a parking service puts up a dummy page with ads. When people visit and click on the ads, that's money for you. This method works best with popular keyword domains that get lots of traffic. In most cases, you will not have control over what ads appear on your domains.