Being an early M157 it most likely won’t have had the check valves and uprated tensioners fitted. So likely it has stretched the cam timing chains. P00016/17/18/19 normally appear when this is the case. It could be a cam sensor issue due to the known oil leak scenario, but that could also have a knock on effect to the ECU / ECU harness. The oil leak could be elsewhere and until checked could be minor, but could be major (another thread is covering this already).
Given the car looks very tired then it’s possible it’s not been well maintained. One concern is that the car can still be driven if the fault code for the timing chain issue is constantly deleted, but it accelerates the damage to the point where the chain could jump, but doubt it has in this case as they don’t mention it not being driveable.
Worse case then budget £4k-£5k for the Timing chain issue. Likely that other parts will need replacing whilst it’s being done.
Oil leak - could be anywhere from £300-£???? Depending on what and where it is.
Alloys all need doing, so to do properly with the diamond cut faces circa £500. Tyres may need replacing so circa £750. The Service is due so anywhere from £350-£1250 if things like gearbox oil etc haven’t been done. Hopefully it doesn’t need paint, but if it didn’t it would still need a good detail at circa £500, plus I’d want that interior totally deep cleaned so another £200. All that aside there are still other items such as all electrics working, aircon working, no leaks / water ingress etc etc.
So worse case it could need £8k-£11k. Best case £2k.
Roll the dice……..