as the seller, the only expenses you have are all related to the disposition of the property. You don't have any expenses related to the acquisition or disposition of a mortgage. So for you, expenses related to the disposition of the property are added to your cost basis of the property. As an example, that would include title transfer fees if you the seller actually paid those fees. (typically, the buyer pays all the property acquisition fees - but not always.)
Any commission paid out of your gain on the sale, is also added to your cost basis. Typically, that's about the only thing the seller can add to their cost basis. If you've got a HUD-1 closing statement, you'll note that "just about" all of the fees related to the transfer of the property (not the loan) are under the buyer's column.
