Times is hard.
It will pick up if and when the property market picks up, people start moving and improving their homes.
I'd recommend he carries plenty of business cards, and has, if not sign-written, at least a Magnetic board on the side of his vehicle, showing his personal or company name and town (e.g. "Jack Jones of Bermondsey") so people will know he is local, and a landline phone no (not just a mobile). Having the logo of his scheme will help, though most people only recognise NICIEC. Leave it prominently parked outside every job and chat to neighbours.
And have set charges for common small pieces of work such as: add new double socket; connect electric cooker including up to 5m cable; add RCD-protected weatherproof garden socket; provide Electric Shower circuit including Henleys, mini CU with RCD, and up to 10m cable. Put these on a handout or have them by the phone. You can say "subject to survey" just in case, but you need a price which in 9 cases out of 10 you can stand by. Always give every satisfied customer a few business cards, and have some stickers made to go on the CU with name, number and a space for "next inspection due on ddmmyy"
Surprisingly, the Parish Magazine (if there is one) is a good source of mostly small local jobs, with the occasional rewire.
Avoid work for small landlords unless they pay in advance. Especially avoid work for landlords' agents.
PAT-ing is awful work, but if he has an automated tester that links to a PC, he can do a lot of appliances in a day. Look out for local voluntary organisations and charities with their own premises. If they have not got a regular electrician he might be able to pick up some testing and repair work. Village halls and the like need to be certified safe. Even if he doesn't make much out of the organisation, getting his name known locally should mean that the members and volunteers will think of him for their own homes and businesses.
Lots of self-employed are very bad at record keeping, invoicing and debt management. This drives them to bankruptcy. Don't be one of them. Don't ever take out a loan secured on the house. If the business can't survive on its own, don't throw your home away with it. Sorry.