You are narrowing down your choice by looking online only. Online, even for 20/30 year old guys, is difficult so for you, it is going to be more difficult. It is possible for you to find younger girls, however are you in a position where they will be attracted to you. Do you have status? Do you have money? Are you in shape? Do you dress well? Have you experienced some cool things in life? All these things are going to benefit you when talking and interacting with a younger girl. Also, you dont have to go out at night to meet these girls. These girls also need to go to the supermarket, libary, shopping etc. You can see these girls everywhere. Talking to them will give you a good indicator if they are interested or not.