Most gateways have a minimum, yeah. Stripe is around 50 cents in most currencies, PayPal also has practical minimums because fees eat it anyway. But “customers in any part of the world” is where people get stuck... no processor is truly worldwide, they all block some countries, high risk BINs, failed 3DS, etc.
@missjennifer if you are selling normal products/services, Stripe + PayPal is still the cleanest combo. If your niche is higher risk then you need a high-risk merchant account, not just a random payment link, because it will get limited fast once volume starts.