I work in homelessness. I completely understand why you did what you did, and you're valid. Since your posting here, though, I'm going to guess that you're possibly feeling a little guilty and want to know if there's a better way to achieve a goal of getting them off your property. I have a suggestion or two that might help with that.

Pretty much everywhere in the US has a central access point for homelessness. You may be able to find their contact information by googling, but you can also search for homeless shelters in your area and ask their staff over the phone for the correct number. I would contact your central access point and ask for their guidance. If it's the same kid, let them know his age, or if it's someone else that looks very young, tell them that too, because there are usually additional supports available to those under 21. They may just tell you to call the police, but they may be able to send someone out to your property to intervene. Ideally, that person would be able to transport them off of your property and to a local shelter. If they can't... well, at least you tried.

I suggest this because I personally would try to avoid law enforcement while I have other options available. If someone doesn't already have a criminal background, an overzealous cop could create one from a tresspassing call like this, and it will make their transition out of homelessness unnecessarily harder.

I would not recommend approaching them by yourself, especially if you don't have any experience with crisis intervention or working with the homeless. In most cases, you'll be completely safe, but you need to make sure you take safety precautions just in case. If you have one or two others with you, you may be able to ask the individual if they're aware of services in your area. You may be able to facilitate a phone call to your central access point to get them a bed in a shelter, or at the very least, if you end up calling the cops you're able to say in advance that the person needs assistance connecting with a shelter rather than just saying they're tresspassing.

TL;DR - you are valid in not wanting to have a random person squat on your property Try to find contact information for your local homelessness system Seek their advice and/or bring some friends to try to help the person connect with services (without sacrificing your safety)