Your team, like every TFM or IRL team, has diversified sources of income. Good rendering depends on your management and partner choice. Your sources of income are:

Competition Prizes

This is the reward in funds that you receive after your matches.  The rewards of league matches are invariable throughout a season, however they increase/decrease from one level to another. 

The revenue of the cups (C.L, C. Union and Cup) depends on the stages of competitions. The more you advance in competitions, the more your income increases. 

Higher-level managers get a lot of revenue from competitions compared to lower-level ones. 

Ticket Sales

Ticket sales are a means of income that depends on the attendance of your matches. Upgrade your facilities and optimize ticket prices according to your level and the importance of matches to increase your revenue on ticket sales.

Other income sources

They are Transfers out, Manager Sponsorship (support), bet rewards and sponsors. Note that optimal management of your team permit you to diversify your sources of income and increase your funds.