How can I get pricing trends for a specific car model?

Depends entirely on your geographic location, ie country and state. In the USA, you can use kbb.com. In the UK, and most other countries, they have equivalents. My DB9 depreciated faster than I spent money maintaining it. I owned it for 6 months, drove about 1000 miles and spent around $8k fixing it. I sold it for $14k less than I paid.

Ouch! Good advise is sometimes hard to take. I expected from evaluating the pricing data more gradual depreciation, but I don't have any data to assess the cost for maintenance. What was the most expensive maintenance issue you had fix? Thanks for your response, Carlos

Brakes (rotors and pads) were the priciest things at $4k and they don't last long at all. They are only available from Aston Martin, not even the Jag XKR parts will fit. I also had 'Check Engine Light' quite often, seat backs that would only move 1mm at a time when reclining them and a number of other minor issues. I went back to Porsches and have been very happy about that decision.