I don't know why the "-ing" form(starting) is used, not the infinitive(start).

Native speaker’s answer
Rebecca
"Starting" here is used as a gerund, which is a word that ends in the "[verb]-ing" form but acts like a noun. You can use this form when you want to speak about things generally, but perhaps the action (verb) you want to speak about does not have a noun form. An alternative for "there are advantages to starting early" would be "there are advantages [for] when you start early." Ex: I'm a huge hiking fan. Ex: There are many advantages to learning how to cook.