I haven`t been demoted before so I`m just throwing out idea`s based on what I`ve seen and read, I`m thinking that you should look to cut salaries to increase your profits as your income streams will obviously be lower. Just keep a team that`s good enough to win your league and bank the profits.
And you should probably drop your arena prices before the season starts as the fans won`t like paying the higher prices in a lower league.