Everyone has different answer. Money you need depends on your life style. But everyone needs one to fulfill basic needs.

In T11, simply speaking, basic needs are players' salaries. Your cash flows should be able to support this. Even if you use the same team forever, the players will request a signing fee and higher salary in 3 years after signing, and every 2 years thereafter.

Your basic cash flows are ticket sales, merchant sales, sponsorship, and maybe match win prizes. The big competition prizes will not be received until your team finished. You can save them for paying future daily expenses. Waiting them to pay daily expenses may cause cash flow problem.