What due diligence to do while purchasing land from Owner directly

[Dee Mandrekar]

I am thinking of purchasing land from an owner directly which also has a small house on the property. What all do I need to look for if in future I plan to use the extra area to add few homes for rentals. lot is 2 acres. 

how do I know what that area is zoned for? owner does not have survey of the land.