4)Why not structure your pre-wires, whether you are doing them or the electrician is doing them (at YOUR direction) so the builder can include several upgrade options to the homeowner and he shares in the profit? No way the electrician will be able to do that on his own. The advantage to the homeowner is they get to build it into their mortgage. The advantage to the builder is extra profit. The advantage to you is that the builder no longer has ANY interest in working with the electrician if you can make him some extra money. Nor do you need to cut your profit. Charge the same as you always would but make sure the builder can add in his percentage. You could offer:
a.A basic volume control package.
b.A multi-zone package.
c.A home theater package.
Make the differences between the packages significant and clear cut so the client sees value in the upgraded options. None of these options require a single extra dollar on your part as long as the wiring is in place. In the mean time, the builder could even have you meet with the client to present the options to them.