[maramizo]

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if (strcmp("/start", cmdtext, true, 10) == 0)
    {
        if(IsMoneyHunting[playerid] == 1) return GameTextForPlayer(playerid,"~r~your already doing the money hunt",3000,3);
        {
            for(new i;i < MAX_PLAYERS; i++)
            {
                GameTextForPlayer(playerid,"~g~moneyhunt started~n~get to the red marker",3000,3);
                new randcheck = random(sizeof(RandomCheckpoints));
                SetPlayerRaceCheckpoint(playerid,0,RandomCheckpoints[randcheck][0],RandomCheckpoints[randcheck][1],RandomCheckpoints[randcheck][2],0,0,0,8);
                IsMoneyHunting[playerid] = 1;
                return 1;
            }
        }
    }
    return 0;
}

Is wrong, you didn't even use (i) instead of (playerid).
Anyway, it should work for all players in the first script.