Ask HN: Easiest way to process payments (starting witho a business entity)

I've got a side project, and I'd like to see if it has legs (image-scale.com). It's a SaaS business. I would like to charge customers for use i.e. get a credit card at sign-up.

After a little searching, it looks like I need a business entity (LLC, C-Corp, etc.), along with a bank account to make this happen.

I am an American citizen, but I currently live in Switzerland.

Best-case scenario, I could find a purely electronic way to sign up for what I need and find a payment processor (I've used braintree in the past). Any ideas?