don't get involved in another one,....
When purchasing a house they or their solicitor should have the common sense to have the vendor declare the alarm working or not, ideally providing a service report dated within the last 12 month.
Control, cable or device -
Controls, does the controls have 12 volts on the aux supply ? (check fuse?)
Device, does the device have 12 volts present to power it
Cable, does the power cable have low ohms when made into pair. same for tamper & 12hr circuit. & high ohms between every other pair ?
Why do I say don't get involved ?
Who do you think there are going to ring on an evening or weekend when there alarm won't set, bleeps too much, does not bleep when it should bleep..... YOU
Find a local proper alarm co. or tell the end user to find one