In my experience, it's best to make the girl pay for her own trip if you haven't fucked her yet. It can be understood that you'll pay for her expenses while she's staying with you, but she needs to take care of a significant portion of the plane ticket herself. If she gives you some good sex, then you can decide to help cover the cost of her transportation if you feel like it or she has genuine hardship. However, as Pitt points out, it's not a hard and fast rule. If she's really hot and fun and you're sure enough that she's DTF to take a chance on it, and you can afford it, then why not? Like Pitt said, you can test her compliance by asking her to stay for a couple of weeks instead of just four days.
I've had girls fly or drive long distances to see me and I did help some of them with their transportation expenses, but it was AFTER they fucked me. If any of them had come and stayed with me and immediately put me in the friend zone, there's no way I would have reimbursed them for any part of their travel.
I've known a couple of guys who helped pay for girls to come stay with them and then the girls friendzoned them and never put out. It was very humiliating for the guys involved. Even if they didn't say anything, you could tell the girl wasn't "with" them because of the body language and demeanor when they were around each other. It was very awkward.
I've had girls fly or drive long distances to see me and I did help some of them with their transportation expenses, but it was AFTER they fucked me. If any of them had come and stayed with me and immediately put me in the friend zone, there's no way I would have reimbursed them for any part of their travel.
I've known a couple of guys who helped pay for girls to come stay with them and then the girls friendzoned them and never put out. It was very humiliating for the guys involved. Even if they didn't say anything, you could tell the girl wasn't "with" them because of the body language and demeanor when they were around each other. It was very awkward.