The Construction Assassination

This mission is a hit on Enzo Bonelli, the contractor who locked down the Mile High Club skyscraper site and runs it on graft.

Gold Coast Development, the builder getting crushed by Bonelli's crooked firm, is the stock that benefits.

When Enzo Bonelli dies, Gold Coast rises sharply on the rebound. Buy Gold Coast stock before the mission, then sell after the price goes up.

Must-have prep (combat & stocks)

You fight armed guards from the ground floor to the roof, then you have to kill a helicopter — show up fully kitted.

RPG (rocket launcher) or Homing Launcher: the weapon for shooting down the Maverick Bonelli uses to leave the roof. Destroying that helicopter also clears the gold medal condition No Fly Zone. The Railgun is only for returning players who transferred an account from a last-gen console, so use it only in that case.

Heavy Sniper & Assault Rifle: your mains while the lift climbs — pick off distant snipers and the guards pouring in.

Super Heavy Armor & snacks: the site is wide open, so you will get hit. Max the armor bar at Ammu-Nation and stuff the inventory with EgoChaser and other store snacks for health.

Before the mission, set the in-game day to Monday morning. (Open save from bed, cancel to pass time.)
Open the phone and put every character's money into Gold Coast (ticker: GCD) on LCN.
Once the buys are in, start the mission as Franklin (the L icon).
At the site, drop the guards from cover and ride the exterior lift up.
On the roof the target boards a helicopter and preps to take off.
Duck behind roof cover, pull the RPG, Homing Launcher, or Railgun, aim at the chopper, and blow it out of the air.
Leave the site to complete the mission.
Sleep to pass the time. About 24 hours later, when the return is around 80%, sell and take the profit.