What do you think about this casual sex idea? good idea?

me and this guy have met a couple times, and he seemed really into me and asked if i would go out with him, and wanted to be in a relationship, i told him and explained i didn't want to be in a relationship and just wanted to be single, and then the conversation went onto no strings attached, and then he told me he actually wasnt looking for a relationship after i said it, bit he said he did before. which i am fine with a NSA, he is verrrrry attractive aswell, he is 18, and i am underage.... opinions? i would make suuure we use a condom because of possible stds, and i'm on the pill