I have never heard of anyone giving away free money on the internet. If they were doing that, I think we would all be rich and have lots of horses!
Perhaps you could ask the barn where you take lessons if they could work out a deal where you clean stalls and feed in exchange for boarding your horse there. I don’t think it is legal for them to pay you cash, but it is legal for you to work in exchange for board. If your lesson barn won’t help, try other local stables.
I know that at some breed association shows (AHA, APHA) they have raffles for horses. Start visiting or showing locally and buy raffle tickets if they are raffling a horse.
Other than that, there aren’t many ways to get a free horse, unless you buy some old broke down thing at the auction for $40.

Before you get a horse, you need to be riding for at least 2 years and have a trainer’s OK. You need to be able to groom, feed, tack, untack, muck, and check for injuries. If you ride western, you must be able to walk, jog, and lope. If you ride english, you need to be able to walk, trot, canter, and jump 1 1/2′ feet. You must also be able to pay for the horse. Board is $200-$600/month. Farrier is about $100, 6-8 times/year. Dentsit is $100-$150. Vet is $300 for the shots and a few hundred for check-ups a few times a year. Horses are expensive. The eonomy *****. So stay with lessons and wait until you can actually afford a horse. Trust me, I know what you mean, I’ve been riding for 6 years and I’m totally prepared for a horse, but with the cost of owning a horse on Long Island, I can’t have one. ***** for me, but not going to happen. I have to wait to get a job. So do you.

The statement in the parenthesis proved that you are not ready. No one is going to give you money for your first horse. Please GET A JOB first (you may have to wait until your 16) You are only 13. Or go to the local barns and ask for a job cleaning stalls to work off a lease. You sound like a know it all that doesn’t really know it AT all.