It's funny, almost all beginners are more or less the same.
But to awnser your question, Im not really shure where you can find carmodels. but you don't need models for that! I belive that there is some car textures in the HL.WAD. Just use those and then adjust the brushes to the textures. I belive they are very good to the r_speeds due to their cheap looks, that means that you can put a whole bunch of them in your map.
And yeah, Im not 100% sure what you mean by:
car models(brush).