So long as it's clear both of you aren't that committed emotionsally and let the other know you're not exclusive at a certain point. I do have a NSA relationship with someone who calls me when she's in a rut and not seeing anyone. If I'm not available, it's not happening. It's not impossible to do a NSA, you just both have to recognize that you're not going to get married/have kids but you both have a blast in the sack. Sex can be healthy for everyone just make sure it's emotionally "right".