You can achieve this by redefining the method GET_VH_PRODUCT_TYPE() in IMPL class of searchHelp view. Just copy paste the implementation of this method from super class and now control the internal table as per your requirement like
comment out the line APPEND INITIAL LINE TO lt_ddlb. (line no: 47)
as it will add an empty line at the starting of internal of product type values which you dont want. In you case there should be some default value for product type field, so arrange the inetrnal table values according to you requirement and what ever value you want to default for product type that should be the first value in the drop down without empty line and add an empty line at the end of the internal table.
No need to call super->GET_VH_PRODUCT_TYPE() in your implementation as you have written all the required code in your implemenation itself.
Hope this would help you!
I didn't understand why do u want to default product type in result list, it should be based on the product you get in the result list.
If you searching based on product type = financing then result list will show you the product type as financing.
But if you are searching based on some other search criteria, it would display you the product type in result list based on your search criteria.
May be you can explain your requirement with the help of a scenario.