I'd say find out all you can about a new customer , including credit check.
A few observations after many years in the trade .
1. Domestic , most older customers have been fine ...about 1% became fly pickers , looking for money off etc .
2. Domestic , the new breed of 30 somethings , often working from home on a PC all day , video conferences etc , smartarses oblivious to the fact that you should be paid 3. Young women , late 20s early 30s who run shops ...don't really want to pay you , imagine fluttering eyelashes will get jobs done for sod all. PITA .
4. Long standing business needing regular sparky , generally honest , cherish them .
5. A new builder phones .... Hmmmm where,s his last sparks , why hasn't he built up a relationship with regular sparks?
6. Worst offenders ... fellow tradesmen who have pulled you in to help ...busy period ...need your experience ... need extra hand .... doesn't want to pay you once finished.
7. Posh people , generally, more likely to rip you off than working class .
8. There are some good honest intelligent builders about but in a minority , most are full of their own importance who think you sit awaiting their call all year round .