Why would a guy who’s seperated invite me to stay at his place?

I was talking to a guy I’ve been friendly with for years and he said he’s is still married but lives separate from his wife, then he invited me to stay with him if Im visiting his state one day.
I’m not sure if it would be right and even to trust him, or if it’s appropriate to stay there, why are they living separately if still married? Any advice would be really helpful.

Why would a guy who’s seperated invite me to stay at his place?
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