I have just learned that using the = operator creates a reference to the original instance of the class rather than creating a copy. What I did to get around this is created a ShallowCopy function:

Imports System.ComponentModel

<TypeConverter(GetType(ExpandableObjectConverter)), Serializable()>
Public Class BoundingBox

    Public Sub New()
        LowerLeft = New Vertex
        UpperRight = New Vertex
    End Sub
    Public Property LowerLeft As Vertex
    Public Property UpperRight As Vertex

    Public Function ShallowCopy() As BoundingBox
        Dim tempBB As New BoundingBox
        With tempBB
            .LowerLeft = LowerLeft.ShallowCopy
            .UpperRight = UpperRight.ShallowCopy
        End With
        Return tempBB
    End Function

End Class
My question...What is best practice regarding custom classes and creating copies that do not refer to the original instance data?