Question: How do Juniors who play tennis earn any money?
About the article "Tennis", section "Junior tennis".

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In tennis, a junior is a player 18 and under who is still legally protected by a parent or guardian.
Players on the main adult tour who are under 18 must have documents signed by a parent or guardian.
These players, however, are still eligible to play in junior tournaments.
The International Tennis Federation (ITF) conducts a junior tour that allows juniors to establish a world ranking and an Association of Tennis Professionals (ATP) or Women's Tennis Association (WTA) ranking.
Most juniors who enter the international circuit do so by progressing through ITF, Satellite, Future, and Challenger tournaments before entering the main circuit.
The latter three circuits also have adults competing in them.
Some juniors, however, such as Australian Lleyton Hewitt and Frenchman Gaël Monfils, have catapulted directly from the junior tour to the ATP tour by dominating the junior scene or by taking advantage of opportunities given to them to participate in professional tournaments.
In 2004, the ITF implemented a new rankings scheme to encourage greater participation in doubles, by combining two rankings (singles and doubles) into one combined tally.
Junior tournaments do not offer prize money except for the Grand Slam tournaments, which are the most prestigious junior events.
Juniors may earn income from tennis by participating in the Future, Satellite, or Challenger tours.
Tournaments are broken up into different tiers offering different amounts of ranking points, culminating with Grade A.
Leading juniors are allowed to participate for their nation in the Junior Fed Cup and Davis Cup competitions.
To succeed in tennis often means having to begin playing at a young age.
To facilitate and nurture a junior's growth in tennis, almost all tennis playing nations have developed a junior development system.
Juniors develop their play through a range of tournaments on all surfaces, accommodating all different standards of play.
Talented juniors may also receive sponsorships from governing bodies or private institutions.
In 2004, the ITF implemented a new rankings scheme to encourage greater participation in doubles, by combining two rankings (singles and doubles) into one combined tally.
Junior tournaments do not offer prize money.
Juniors may earn income through tennis by participating on the Futures, Satellites or Challenger tours.
Tournaments are broken up into different tiers offering different amounts of ranking points, culminating with Grade A and the junior Grand Slams - the most prestigious junior events. 
As the governing body, the LTA’s overall purpose is to continue to grow and sustain the sport.
The success of British tennis is tracked by five headline measures of success:1.
Number of members of registered places to play 2.
Number of British tennis members 3.
Number of regularly competing juniors 4.
Number of International A Matrix juniors 5.
Number of players in the top 100These measures of success gives a regular snapshot of the impact of work the LTA does and helps the organisation understand through trends the progress over a long period of time.
The LTA’s focus is to develop participation growth to help more people play tennis.
The approach to growing participation is based on investment in four main areas:1.
Places – Investing in places to play at parks, clubs, schools and tennis centres 2.
People – Supporting the people who make tennis happen, including coaches, volunteers and club officials 3.
Programmes – Developing programmes including LTA Mini Tennis, Cardio Tennis and Tennis Xpress 4.
Promotion – Bringing together the places, people and programmes to show how tennis is a fun affordable, family sport which is a great way to get fit 
Junior tennis refers to tennis games where the participants are aged 18 and under.
Eligibility to compete is not based on age, but year of birth: as a result, some players must move out of juniors soon after their 18th birthday, while others can play juniors until they are nearly 19.
Some players who qualify as "junior tennis" players also play in main adult tours, though forms signed by their parent or guardian are required for this. 
Source: World Champions Juniors at ITF Tennis.