Getaway Vehicle (The Big Score)
Acquire a vehicle you wish to use as your getaway ride during The Big Score (Obvious Approach). Any vehicle is fine, so long as it is not the personal vehicle for either Michael (Tailgater) or Franklin (Buffalo). It must also seat a crew of four; fortunately the game will gauge the suitability of your vehicle while you are entering it.
Once you (and the game) are satisfied your getaway vehicle, bring up your cellphone, locate Lester's name in the list of Contacts, then choose "Getaway vehicle ready."
Now follow the directions to park your getaway vehicle in the underground parking lot of the Arcadius Business Center, directly across from your target: the Union Depository.
 Conditions for failure
N/A for this mission