Retrieving data from a storage buffer

I am setting a up a storage buffer and then using memcpy to pass data to it but when I try and get the data back from the buffer I am getting junk data.

	Buffer payload_buffer;
	VkDeviceSize buffer_size = sizeof(float);

	// Create the data that will be saved
	float payload = 5.0f;
	// Move the data to the GPU
	memcpy(payload_buffer.mapped_memory, &payload, buffer_size);
	// Move the data back
	memcpy(&payload, &payload_buffer.mapped_memory, buffer_size);
	// Output the data
	std::cout << payload << std::endl;

	// Destroy the buffer instance
	DestroyBuffer(engine, payload_buffer);

I am making sure to use vkMapMemory and this is located inside the CreateBuffer function. I am really not sure what i’m doing wrong as i use this CreateBuffer for the rest of my application without fail.