If you are going to do it, I would focus on Lutron Lighting, Shading, Sonos/HEOS, and networking. I wouldnt get into the prewire business, and would minimize the retro aspect as much as possible using the above mentioned brands wireless capabilities.

You are going to want to minimize your exposure to service intensive products. Lutron lighting and shading just work, Sonos and HEOS just work, quality networks just work and are a necessary evil anyway.

What you need to ask is do I want to do 10 10k jobs which generate upto 10 referrals or do I want to do 1 100k job and have it suck the life out of me and get upto 1 referral, then constantly service the 100k job for various shit that is out of your control eventually souring your relationship with said client.

Have you thought about the plumbing industry? It pays the same and you connect 2 pipes together and they never call you again. IF they do call you to unclog the pipe there is no expectation that its a free service call. You will never hear "It never worked".