theres a fast way to get $1 billion+ in the SP campaign, i'm doing it right now in the beginning right when i switch back to michael. basically bring up your phone (up arrow on ps4), go to internet browser, click on money & finance, LCN exchange, markets, and sort by the last column % changed and click on the one with the biggest down percent (red), and buy max shares - yeah you have to hold down the button on the + until it maxes. then click on the share name itself in the my portfolio tab (DONT click on sell all, click on the stock name itself first), click sell, then sell all and you should skim 20% or so off the total value. click back on markets, sort by last column, rinse and repeat.
repeat a couple dozen times and you'll be up to $1b within 30 minutes, no need to bother with the assassination missions manipulations etc. can swap to all your characters and do it, i'd cap at 1b as the game stops counting past 2.1b.
