Usually a guy wants a woman for sex if they suspect she will give them sex. That's why the old advice of not getting too intimate too soon can actually work. If he's interested in only sex, he won't wait. If he is interested in you for more than that, he will. You just have to watch for people who are manipulative and lie to get what they want. That's why it's so important to be true to yourself and your values and not be talked into anything if it feels like it's going too fast. If you want only sex too then of course that's fine. If not, it's probably best to wait until after you've dated for a while.