I'm a SaaS Startup. Can do sales without incorporation?

Hello Founders! We just got our 1st paid customers but I'worried whether we should incorporate immediately or not. 1. Should a SaaS Startup be incorporated in order to get paid through Stripe/Paypal/Credit Card, legally? 2. Is there a threshold of being not exactly legal? 3. Is there any like "Umbrella company" service to pay the taxes for you, without needing you to incorporate?