Now what? You of course do not want to lose the sale and just reserving something doesn't mean they will come through with the month. (been there done that I'm afraid.)
You will need to do a few things to get started.
First, you will need a PayPal account. If you have one already, make sure to set it up as a business account. That way you are sure to be able to create invoices.
Second, you need to go into your payment account on Etsy and make sure you have selected "other" as a payment option.
Go into "Finances"... then to "Payment Settings" and at the bottom click the circle to turn on "other" for a payment option.
This will allow you to process the sale via Etsy and use their discounted shipping too!
Now is the time to work out the payment plan with your customer. I suggest getting a deposit to start with. (I'll show you in the PayPal section later on.) You will need to note your customers email address so you can send your PayPal invoice to her.
Next, change the listing to "reserved" so it isn't purchased by someone else. Put it both in the title and in the description.
Next open your PayPal account. Look for "Create Invoice".
An invoice form will come up and you just fill in the blanks! You can click "allow partial payments" if you are allowing your customer to pay a little over time. You can even set the minimum payments allowed. Just make sure to talk this over with your customer.
Anyway, fill out the invoice and input your customers email. I always look at a preview to make sure all the info is correct. Once it is correct, hit send! That's it. And every time your customer pays money via her invoice, PayPal will send you an email.
PayPal will keep track of the payments and update the invoice as your customer makes payments.
Once the item is fully paid for your customer then goes to the reserved listing and pays using "other" as the form of payment. Then process the order just like any other order. Etsy gets their commission, you get to take advantage of their reduced shipping and it counts as a sale for you.
Hope this wasn't too confusing!