To turn off the cap in a franchise you already have started get your team extremely close to the salary cap (100k to 0k works for me) but you have to be missing a player you need (ex. have only 4 WR) then try to go to a regular or pre-
season game it will say something to the effect of "You need a WR" then give you a choice to sign one or have the CPU sign it, choose CPU. Then it will pause for a second and say "no cap room choose cancel to sign player yourself or choose ok to turn off salary cap permanently. "Its that simple warning though this will turn off owner mode for good