Unsure if something to buy online, eg an apartment. Is a scam?

Many of us buy from classified ads. Eg: Looking for apartments in a new city? But now the person can be a scammer, so how you can understand that he is using the correct image or fake. Make sure to Reverse image search any images to avoid scams. Just Upload your image or find through url. Using http://www.image-search.org/simply.