I didn't have much problem coming up with a money tip. For me it's simple – get all the money up front. I never send out a letter unless the money is in my bank account.
So that customers know what to expect, I have made it clear on my site that letters are to be paid before they are sent out, and the latest date they need to be paid. There were a couple of customers who wanted to pay after the letters were sent out, and I just told them that the letters would be sent out when I had received payment. They ended up going somewhere else!
I decided on prepayment because I didn't want to be wasting my time following up on a $15 payment.
To make it easy for customers, my sign up page redirects people to a payment page where they can pay with PayPal or direct deposit. This way they can pay when they place their order. This way I don't have to chase them for their money and I have the money in my account to pay for envelopes, stamps and everything else I need to prepare and post letters.
I know this won't work for everyone, but it works well for me.

One of the things that I did last year, quite by accident, is to keep a database of the names, addresses and email addresses of the parents who bought letters for their children. Currently the database is quite small, only about 15 families, but it's a great start.
Ho ho ho, my name is Natalie and I'm one of Santa's helpers. Last year, Santa invited me to help him write letters to children. Along with my friend Quinn, we had a great time creating and mailing letters to children all around Australia. So much fun, in fact, that we are preparing to do it again this year. I'm so excited Santa asked us to help again.