You can generally work out these people who are after "mates rates" just add 10 % and then give them a discount.
TBF many now are stuffed by the internet. Bring asked to fit substandard kit, even possibly stolen. Supplied by the client, I say no. End of.
Because you know when it goes wrong, and it will. The phone call will be along the lines of "That stuff you fitted has stopped working".