Its pretty hard to get full sponsors. I have a shop sponsor that pay for over 2/3's of my labor and a paint sponsor that is painting my car for near free for what its costing me.
I was in your same place when I first got my car. Not enough money and to many mods to do.
I am sorry to say but most sponsors will not look at an 18 year old for the fact that they want some one who is going to be able to commit there selves to there cars. Not saying that a younger guy like your self cant but for the fact is most of them are busy with college and such or just getting started there not going to have the time to go to the track every weekend or every show there is around there area.
The best thing to do is not to try to sale your car but sale your self per say lol. Not litterly but just go out to all the shows and meet people and they will be more then likely to help you out.
Sure they might not give you a free paint job or motor but it will make it easier for you. When I blew my motor to pieces I contacted MMR after talking to them at a few tracks and they were more then willing to help me out. Sure I did spend BIG $$$ but for what i was able to do I got more then what i should of.
Network your self prove to people that your here to stay and your letting your self be seen. People wont sponsor a street cruiser or a weekend warrior they want the real deal and thats where you have to prove your self.
It also helps to have a good start on mods as well. i had my complete cervini's kit and wheels before people looked at me. Its all based on who you know.
I AM NEED OF A TURBO SPONSOR WHO WANTS TO SEE A T-80 in my car