How low of an offer can I suggest for this car?!!!?

I've asked this question like 2 other times but I'm not getting answers. I want to buy a vehicle and it would come out to about $31,000. Assuming I have $31,000 in my hands right now, if I drive down to the dealership how much is acceptable to offer. I'm looking for answers like $29,000 in cash is the lowest you can offer. Or it's not fair to offer $20,000 because it's too low. Please! lol