As already covered by now, you aren’t legally allowed to make money off of episode assets. So character cards aren’t something that you can charge for.
Their avatars, clothing, tattoos etc all belong to episode, so if you really wanted to do character cards, they wouldn’t be able to be connected to episode imagery.
I’m not sure where PayPal doesn’t work in the world to be honest lol. So I don’t know what other payment options might not be supported where you are.
Most people prefer PayPal because it’s the safest way to exchange money with someone. Buyers and sellers can be protected by PayPal money guarantees. When I was doing commissions, I worked strictly with PayPal, and all of my customers used that as their method of payment by default.
Nowadays Kofi is another way that people make payments. I believe Kofi works through a link with PayPal and something called Stripe. Perhaps that is an alternative way you can work.
Western Union is another one.
Also, different people approach the manner of payment in different ways. Some people request the fee in portions. For example, with art, 50% upfront, and 50% upon approval of finished piece. Some request it all up front, and others, all on completion. It differs, and I think depending on what you’re offering, a different approach benefits different things.
As to the actual process of doing commissions, you need to have everything in place, and really be thorough about what you are offering, and how much.
Work on your price list to ensure the fees are fair and worthy of the time and effort that you will put in.
I did art commissions, so I can’t say I’m familiar with fees for proofreading, I know many people do it for free, and with many free apps etc, then your work needs to be spot on and of very thorough, high standard. You have to be very good with punctuation, grammar, the author’s language, alternative spellings (for instance, British English, and American English), you need to understand plot development and be able to offer quality work which will assist and potentially improve someone else’s work.
(This isn’t me saying that you’re not able to do this, just explaining that as someone would be paying you, they are basically hiring someone as a professional, in which case a certain standard is expected.)