Hey Erick,
Here's something you can use on your yellow letter to find investor/buyers. It should help you get started. You can switch it up as needed.
Hi, my name is _______. I wholesale houses in __________. I have a property that I need to get rid of near the one that you own at _________. This property is priced way below market value so you could either keep it as rentals or fix it up and sell it for a profit. I'm looking for an investor/buyer who can pay all cash and can close quickly. You can see it and others I have available by visiting my website at www.yourdomain.com or by calling me at 555-123-4567.
Thanks,
Name
P.S. My wholesale properties usually sell within 72 hours, so if you're seriously interested, please get back to me ASAP!