i aggree with the 'loud music' playing in the car im in, it can give you a headache quite fast, but at a reasonable volume it is great.
about the boot rattling, yeah i hate knowing that i sound like an idiot especially while im trying to actually enjoy my music...i tend to crack the windows so they dont think something is up with my car/boot..
and i was mainly referring to getting out, opening the car and boot up and turning it up for a reasonably well put together sound for a gathering outside the car.
well imo that is reason to spring for it; if he doesnt like it, he isn't going to go "HEY EVERYONE, JJ72 (idk your real name ) MADE THIS SKIN I DONT LIKE"
the worst that happens is you have one 'bad' client that you cant agree with on a design. the best is you make a successful client who loves your work.
weigh the positives and negatives, and decide if your time is worth it.
EDIT: ok ignore my posts, the posts after me make some nice points
either way it is publicity, large publicity at that. if somebody hears about you, sees your previous work, and likes it, i dont see why they wouldn't want to hire you...i say take the risks life throws at you if they are worth taking...good luck mate!