@LBad96, it is more mixed because colleges do base on zip code. Coming from a wealthy district they may assume the kid has access to the same resources, tennis etc. Obviously if the parents did not complete high school, immigrated, work as maids in the local hotel yes, they will give them the benefit as ^.
If it is less obvious, they may be cut less slack which will hurt them but also will be assumed (in need blind schools) to have less or no need. This part will help them, since it is less of a financial risk for the school. While no need blind school knows exactly how much need a student has, most schools can get a sense from zip codes, parents occupations and ECs.
OP, tennis as an essay topic can be cliche, especially if you will not be recruited. However, PAYING for tennis may not be. However, it would have to be done very carefully and will depend on when your essay hits. If it hits after the kid who has been helicopotered his whole life you would be fine especially if YOU were the one responsible for paying for tennis. If you happen to hit right after the kid who escaped from some oppressive regime and he, his little twin sisters and his single mother have to live in a homeless shelter while he does his intel project, it will not work.