Selling a second home

Hi to all cave forum members.
Please can someone help with some information.
We invested in a property to reform and sell approx 10 years ago and slowly fitted it out ready to put on the market. We will not name the solicitor that we have been with for past work as we could be liable.

We now have someone that is interested in the cave house for sale but living in the UK. We approached our solicitor for information as we have never sold an investment property before.
The solicitor stated that we cannot claim back the purchase price of 10,000 euros when we bought the ruins to reform. Then we paid VAT/ IVA On all materials to reform the cave,so basically we done everything totally legal/inc escritura etc with a view to put all reform costs and purchase price against CAPITAL GAINS TAX.
The solicitor says that we cannot claim back or offset the above against Capital gains tax.. Surely this is not correct..Nothing is sold until you have the money in your bank but can you advise on this problem above..
Last thing please Can the English potential buyers buy with just a passport or do they need NIF number and where would they get one if needed. Obviously they would need to set up a Spanish bank account as well'
The practice in question has full English translators so no mis-understandings.
Thank you

Just thought. Maybe PM Message might be more appropriate to some members. Thank you

This is far beyond the competency of a group of ex-pats to answer.
You really should engage a spanish accountant to deal with this matter on your behalf.

On your second point: yes, they will need an NIE. It's quite easy to obtain. The best route is for them to have a gestor do the work for them.