If taking payment in cash, require that as much as possible be in $100 bills. The current $100 has many security features:
https://d39pc38av48c2g.cloudfront.ne...3_Features.pdf
(or load from
https://www.uscurrency.gov/security/...s-2013-present if that .pdf link doesn't work)
Some municipalities have setup "Craigslist exchange" locations where there is active security so you can meet to close a deal. You may want to search in your location to see if they have a location/initiative like that.