This quest starts immediately after Double Life ends, although unlike many main jobs, you’ll get a reprieve before this one truly gets going, as you’ll have to call one “Mr. Hands” to set things in motion. Call Mr. Hands and you’ll get a decisive “I’ll get back to you”, after which the job’s objective will change to, and we’re paraphrasing: “do other stuff until Mr. Hands calls back”. If you’ve done quite a bit of side content already, this could happen if you just leave your game idle a minute or so, otherwise, considering working on something else. If you’re dead-set on pushing the main story, starting Ghost Town isn’t a bad idea.
After you get the call back you’ll need to head to a chapel in Pacifica, which fortunately has a fast travel terminal outside you can make use of, if you’ve already discovered it for some reason. Drive down there or fast travel, then head inside (you can rest on the railing if you’re here too early/late) and work your way through the crowd to meet your contact, who passes on some instructions.
Make your way to the nearby butcher shop (it’s around 70 meters away - you can just walk there) and talk to the vendor and follow his instructions to meet Placide. Walk and talk with Placide and he’ll lead you to his office; Your responses and reactions don’t really matter here, you’ll get details on the job, after which this quest will end and the followup, I Walk the Line will immediately start.