To really make it driveable (not just a beater or something) you'll need to sink at least the following stuff into the car:

-Windshield
-Time and cost to fix the climate control.. anywhere from $5 (fuse) to $2000 (everything including the compressor). I would guess high.
-Rear wiper motor - not too hard if you can find a junkyard or eBay part
-Tire wear is likely just an alignment if the suspension looks good and the car hasn't been hit.
-Oil pressure is the big thing.. you are gonna end up putting a motor in this car, sooner or later.
-Oil leak could be the rear main seal which is much $ and not really an easy DIY job.

So if you want to drive it "as is" it's a deal. Start fixing things, and you could easily end up $6k in the car!

If it were my car, I'd replace the windshield, fix the climate control without A/C working (get the blower and heater working), align the car, and tinker with the rear wiper motor. All relatively easy stuff to do. Then just keep driving till you kill it (likely from no oil pressure....)

My bigger worry is this: If the previous owner hasn't been driving it without a proper windshield, rear wiper, working climate control, and wierd tire wear, what else is going to go bang? He obviously hasn't spent much money on the car in the last few years!!

__________________
'83 300SD 335,000km (207k) mi SOLD
'87 560SL 163,000km (101k mi) SOLD
'86 300SDL 356,000km (220k mi) SOLD
'92 500SEL 250,000km (155k mi) SOLD
'90 300SL 140,000km (87k mi) SOLD
'01 S430 260,000km (161k mi) SOLD
'03 SL500 167,000km (104k mi) SOLD
'07 S550 4MATIC 235,000km (146k mi) SOLD
'07 GL320 CDI 4MATIC 348,000km (215k mi)
'13 GL350 BlueTec 4MATIC 170,000km (105k mi)
'14 SL550 72,000km (43k mi)