Anyone can post an ad on Craigslist, so proceed with caution. There are so many apartment rental scams run through craigslist, that the site has a list of scams they continue to update!
Just because someone has the keys to an apartment doesn’t mean they have the right to rent it out, so do your homework. In New York City you can verify owners of property on nyc.gov/acris.
It’s always a good idea to ask lots of questions of the person showing the apartment. Also, be sure to speak to other tenants in the building and ask about the quality of the management of the building. If you have doubts about the building or the person claiming to be the landlord, don’t rent the apartment.