the initial basis to the donees for a gift that is sold at a gain is the donors basis at the date of the gift (that would be the $13.5K plus any improvements from the date they bought it to the date of the gift). To that you can add the cost of improvements made since the gift. from the gross sales price, you can deduct the costs of sale which would include but are not limited to transfer taxes, sales commissions, warranty deed, and certain credits given to the buyers at closing for things like their closing costs.
