You take 3500 and in 30 days switch to local credit union. Its legal and costs you about$100. You get 1.99 or something less than 3.5 for sure. Thing is if you went with 500 deal you lose 3 grand instantly... With a loan who knows if you get a bonus or are able to prepay a litttle in the end interest will be low.
if you have the option of heading to another dealership i say you just walk away when they pull this stunt