I'd like to buy an iso, but I don't want to use a creditcard, prefer to use PayPal. How to go about that?
Just download it as free of charge (like @ourfor's said), then head to this, where you can choose PayPal as your payment. Also refer to @AlphAShOOt's answer, you can become a Patron too to support elementary OS.
In my experience, I did download it as free and pay using PayPal.
Hope it helps.