It depends on what you mean by "building" a car. There's more than just mechanicals. Other than that, you have the body, interior, suspension etc.
If you're going to start tinkering with your car, I suggest you firstly buy a workshop manual, and get assistance from someone who knows what they're doing.
Turbo'ing an engine that wasn't designed for a turbo means lotsa dollars, as the drivetrain, suspension and brakes also need to be upgraded.
Start off with the easier jobs, then work your way up as you gain experience.
Money and know-how are your two biggest challenges.
Best of luck.