Guy flirts with me and spends the night at my house.. then propositions my best friend!?

He spent the night at my house, but nothing happened. I think he actually likes and respects me.. but then he goes and asks my best friend if she would have with him! I have suspicions that he may be using drugs, which might account for his actions. What is going on? Sorry this is more of a rant than a question, but I'd like to hear your comments! Is this typical behavior of a normal horny, twenty something man?