RFID + Lotus newbi

I am completely venturing in to the unknown on this. I am a model railroader and want to use the RFID sensors to track my engines around the layout. I have watched a YouTube video that does exactly what I have been trying to figure out for years. As I have no idea how any of this works so I will be attempting to duplicate his set up exactly.

My questions: can multiple RFID sensors be hooked in to the lotus he is using? I am hoping to test it with three sensors to start with. But eventually if it all works expand in to the dozens, is this possible? How far apart can the sensors be from the central point? I’m looking at approximately 5 meter spread. There is commercial prebuilt systems out there that start in the hundreds of dollars. The SeeedStudio RFID readers and a lotus to connect them is much cheaper. Am I missing something important?
Thank you for your time