Is it important to model a car to be subdivided in all quads or will tris work? Merry Christmas Everyone

I'm having a hard time modeling a car.
My true question is, is it a must that my car model will be made only of quads? I tried this method but it seems like I'm creating unnecessary vertices than I should. I understand that it is crucial for it to be all quads instead of tris if one is aiming for a clean edge flow.  

After I model the car I plan on adding a subdivision modifier. So should I use triad on places that it is required or should I use quads to manipulate my way through disregarding the extra vertices it will generate? 

I'm so stuck. These page was intended by me to have all the problems I'm experiencing outlined, but I leave the rest to whosoever that can give me a way throughout my issues. [sigh] help please!
When tris get subdivided, they become quads. Use tris in your mesh sparingly. 

 

At regular intervals or when you're finished with modelling, you must check for double points in mesh before unwrapping or rendering. To do that, select entire mesh, press W and remove doubles. Note: Doubles occur when you use mirror modifier. So always remember to remove doubles before ever rendering - otherwise you will have rips in rendered mesh. 

Whenever I get stuck on topology, I always go to Pinterest for ideas - TONS of ideas and sources for inspiration. If you haven't got Pinterest, it is time that you start a new account there. Pinterest is where you pin pictures to your boards: those on topology, node compositing, alpha brushes, etc. 
In this link, my board is called Mesh Studies and I collect others' topology works. I have those for hands, feet, faces, etc. 
https://www.pinterest.ie/ritag2/a-mesh-studies/