Finance a 30k walk out the door car?

im 23 yrs old and I have bad credit but I was thinking; if I have 10k for a down payment on a 30k car will a sales person let me walk out the door with the 30k car? meaning that the other 20 k will be paid by me in payments probably over 4 years plus interest. Do you think its possible? I will be making around 25k a year and the job will be dependable.