Ask HN: Best way to accept payments for a product over a term

I have a product we currently sell locally and are planning on taking nationally. Right now we only accept paid in full via credit card or ACH debit but we would like to be able to accept payment over a term (6 months / 12 months) which is often requested by our customers. Is there a good service that provides this functionality? What if any experience can you share about how to do this?