This car is a decent profit but as it is usually a three star car, the purchase price plus potential repair cost eat away at the profit margin. The Salem Spectre is also a fairly expensive car to purchase.
Purchase Price: $43,604
Repair Cost: $10,207 (+/-)
Sale Price: $80,502
Profit: $26,691 (+/-)
As you can see, the Salem Specter does make a good profit when rebuilt in Car Mechanic Simulator 2015.
Rebuilding vehicles for profit in Car Mechanic Simulator 2015 is by far the most profitable activity in the game, assuming that you're picking the right vehicles. Of course a solid supply of spare parts helps too. Here are a few links to additional information that can help you get started in the Car Rebuilding side of the game. This will help you improve your overall game experience:
Rebuilding Guide with Cost vs Profit for all Vehicles in Car Mechanic Simulator 2015
The Auctions Center - The place you buy vehicles
Complete Series of Vehicle Rebuilds for Car Mechanic Simulator 2015
Tunerz Paradize - The place to get special parts to trick out your rides