Dynamically declare a type for a method out parameter

I am struggling to describe this problem I have, but here it is:

Suppose I now have the type of a property on one member of a class (instance):

 Type t = propertyInfo.PropertyType;

How do I declare or setup some variable, in order to receive a method call result later, using the out keyword?

t value; // Obviously doesn't compile, How do I declare this?

// or this?
//var value = default(t); // doesn't work

someObject.GetData(out value);

The premise here is that I don't own someObject and I am stuck with this method call signature.