Loren Baker: Pull a rankings report in SEMRush for Craigslist.org and then exclude the term "Craigslist" ... then search that report for terms your local business competes in. Export those terms and then set up a location listing in SEMRush tracking those terms. Will give you a great idea of how CL ranks in your area and which listings are cat pages or ad pages. Then list your ads there and SEO the ad content to get them ranking in the SERPS.
Rob Woods: If Craigslist outranks you, make sure you rank #1 on Craigslist (or are the most optimized). Same goes if Amazon, Yelp, HomeAdvisor, Capterra, Zillow, etc. outrank you. At least make sure you outrank everyone on those platforms.
Dan Bell: found similar on reddit - and basically allows for double listing on 1st page where reddit listing links to page or url posted