I bought a homemade boat similar to that one several years back. Our state had a provision for titling a homemade boat, even gave me a serial number for it. I went to the hardware where they make nametags to put on dog collars and had them stamp my serial number on a tag and attached it to my boat along with the registration numbers. I would think most states would have a similar process. In SC you have to register any boat that has mechanical propulsion, even electric motors.
Incidentally I paid $150 for mine. It was wooden but looked similar in size and shape to this one.