Add map locations. Each map location can belongs to proposal or budget investment.

app/models/budget/investment.rb

@@ -27,6 +27,8 @@ class Budget
     has_many :valuators, through: :valuator_assignments
     has_many :comments, as: :commentable
     has_many :milestones
+    has_one :map_location
+    accepts_nested_attributes_for :map_location
 
     validates :title, presence: true
     validates :author, presence: true