I am curious how long it takes for me to receive a payment and what form I should expect to receive it in. I sold some shirts early November, and I am wondering how the payment cycles work. Also I am curious of the functionality of Amazon Merch. Can't I start a t-shirt business solely under Amazon Merch if I want?
Early November purchases should be shipped to the customer by the end of November latest, in which case you should receive the payment in first few days of January. The dashboard interface could be clearer, as it is hard to find things, but at the top right hand under 'Resources' you will find FAQ
https://merch.amazon.com/resource/201846470 which has payment details. You could start a t-shirt business solely under Merch, but you need to consider carefully that your entire business is at the mercy of whatever Amazon decides, which is not a very secure position to be in, but it could be a way to get familiar with things.