I wanted to write about this because I see this question come up a lot.
So you’ve got your items posted on Facebook or Instagram and Suzie sends you a message. “hey! I love your super awesome item. I would like to have one of my own.” Then you have an uh oh moment. Breathe.
Decide which payment processor you would like to use. There are many at your disposal, do the research, and pick one. Paypal and Square both allow you to send an invoice to a customer’s email address. I recommend using more than one. Some people will object to using anything other than Paypal. I have also had customers outright refuse to pay with Paypal. Cater to your tribe. They will appreciate the extra step.
Once you have picked a payment processor, go ahead and invoice your customer. I recommend getting the full payment upfront. People flake. When I first started I lost so much money on custom orders that people never picked up. I always get full payment for custom orders. For orders that are not custom, I will take a deposit in some cases. Generally, the deposit is half of the total cost and is non-refundable.