The taxes that you will pay will depend on how much you are selling the property. If the purchase price is more than the zonal value of the property (as determined by the BIR), the purchase price will be the basis for the taxes. If the purchase price is less than the zonal value of the property, the zonal value will be the basis for the computation of taxes.
The taxes that will be paid with the BIR are (1) capital gains tax (6% of the purchase price or zonal value whichever is higher); (2) transfer tax (1.5%); and (3) doc. stamp tax (.5%).
There is also registration fees to be paid with the Register of Deeds once you secure the Certificate Authorizing Registration from the BIR.
The capital gains tax is usually shouldered by the seller. On the other hand, the transfer tax, doc. stamp tax, and registration fees are usually shouldered by the buyer. In any case, the parties may agree otherwise.
Of course, real estate taxes (amelyar) of the property must be updated.
Filipinos are very resourceful if they want to minimize the cap. gains tax, doc. stamp tax, and transfer tax.
Regarding your question "Do I have to pay 50,000 Pesos for the Deed Of Sale and would have to pay half of the closing costs?"
Php50,000.00 for a Deed of Sale and its notarization is too expensive. You must be referring to the taxes to be paid in order to transfer the property in the name of your sister.