I am trying to add a custom body field to a purchase order transaction form, the intent is to display the vendors address, is there a specific field type I should be using for this? Not sure this is the correct channel or not, however, if it is the wrong channel please point me in the proper direction.

there is no specific field type for addresses. Use text area field and sources it from vendor record. That means when you select a vendor this field will automatically updated with vendor's address from the vendor record. As a best practice make this field disabled so no can change it by mistake.

We can add custom entity field in text format to the purchase order form. Then by creating workflow we can populate the vendors address.