At what point can you be sure someone won’t ghost?

I know this is hard to answer without being able to predict the future. However, with dating sometimes you’ll go out with a person a few times, maybe have sex ,and then they disappear. They tell you all the things to keep you around just long enough to get what they want and then leave and move on to the next person. What are some red flags that you’ve experienced prior to someone ghosting you? And at what point do you feel like a dating relationship is in the safe zone and there won’t be any ghosting by either party but instead a relationship?