hi would appreciate any thoughts, insights from the experts in here...

already inspected the car worth 230k vios model 2006, used as hotel transport service. the mechanic though, noted of some flaws such as scratch, slight bumper damage, few rusty stuff in the compartment, and oil leak, which according to the mechanic of the seller is perhaps due to misalignment of the newly installed silicone, so, my mechanic asked to put a gasket (just quoting what the mechanic told me, i have no idea about car stuff), finally all wheels are of poor condition, needs to be changed. we didnt have the chance to lift the car and test drive, but the mechanic assured that the engine is intact.

Question1.
since the price is negotiable, considering above defects, do you think i can haggle to lower it down to 180k to finance repairs and set up.
Question2.
is it proper to negotiate thru phone since i already viewed the unit?
Question3.
what are the documents i shall receive from the seller?
Question 4
should i only pay upon receipt of the legal papers?

any other things i should bear in mind, are highly appreciated.. thanks folks.