The microclimate is a real factor
Sintra's mountain holds mist and moisture, and managing it is a genuine part of ownership here.
Ask specifically about drainage, ventilation, heating, roof condition and the history of any damp remediation.
Character usually comes with a project
Historic homes and quintas often need structural, roofing, electrical or licensing work. That is not a reason to avoid them. It is a reason to price them honestly and budget a real reserve.
Confirm what has been legalized, what was altered without permission and what a technical inspection actually covered. The gap between charm and cost is closed by documents.