What Does He Mean By This?

There's a guy who I know likes me, but he said, "You're living rent free in my head at times." What does that mean? Good or bad?

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So, I went back through some of our conversations, and this text I completely forgot about came up. It looked just like this, "You can start charging the rent for living in your head space 😉."
This text was before the one I first asked about. Any idea what this means?
What Does He Mean By This?
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