There's something extremely important, which is changing in the name of the buyer under 35s all the supplies contracts (electricity, water, gas, phone, etc.) and local fees (waste and sewage fees, IBI, etc.).
Junta de Andalucía is examining these transfers and, if the supplies are not change, they understand the buyer is not using the property for his/her own living, and then they declare void the tax benefit, they fine you and claim you to pay the additional 5'5% saved, plus penitential interests of 20%.
We know real cases.