I personally would ask him not to start it at all on the day of collection you need to start it from cold after standing all night if there is any sort of misfire on start up from cold which clears after say 45 seconds its 99% got head/liner problems

also make sure it has antifreeze/summer coolant if no signs of either its been topped up with tap water regular. although this is not really advisable remove header cap dip your finger in & taste it, it should be sweet & bitter

& swill your mouth out with a 50p bottle of water