Do I hold or sell ??

[Anthony David Quinn]

Hi all, 

I currently own a single family in New Haven. The plan was to rent it out and house hack a small multi family as our next investment. However, we received a call from an investor offering us pretty much double what the house is worth. 
I can’t understand why? 

If the offer is legit is it a no brainer to sell and walk away? How do you gauge when it’s better to sell or hold as a rental? 

Thanks 

Anthony