My son uses a simple slip, which he puts through the door with an SAE, and most people send a cheque through the post.
Thats what i use, and bank details.
i have not been out collecting since my first month doing this job, i hated it, it was another job in itself....
they pay on the door..or use the above, once they are all trained up to this method , they get used to it and its simple......
just adding paypal to my website soon, thats another option....
Gary