Ask HN: Payment gateway for multi-vendor marketplace as an early stage startup?

I’m in the process of building a relatively typical e-commerce marketplace: vendor creates account, lists items, sells, platform takes a small fee. It focuses on a large and underserved market, a domain I know very well, and I’m excited to use it and share with the community.

I’m having trouble getting the payment piece sorted and I’d love to hear experiences and thoughts from anyone who’s been through this before.

My first choice for a payment gateway is PayPal, particularly the PayPal Commerce Marketplace. PayPal is already ubiquitous in the world that I work with. The sole large company who serves this space also uses it so it will make for an easier pitch to get folks to try my product. PPCP is a program within PayPal, the only on-ramp appears to be a form that you fill out and hope to hear back from someone. I spent all morning try to reach someone on the phone and struck out. I’ve been advised that they won’t talk to you at all if you don’t have a plan to reach $2M in the first year and an established business presence. I, a solo first-time founder (but no stranger to early stage startups), have neither a plan to reach that revenue immediately nor an established business to leverage. I’d like to focus on my product instead of pitching to PayPal.

Stripe Connect looks like the best alternative but it will make it harder for me to attract merchants. I’d need their Express product, which comes with additional fees. Their payout approach looks more expensive than PayPal and I’ve been told their merchant onboarding isn’t as pleasant.

Others? There’s Adyen, who I’m told won’t talk to anyone sub-Series A. Braintree seem to have closed their marketplace platform product in favor of PayPal’s. Square has limited support in Europe, where many of my merchants will be based.

I’m getting the impression that this is a domain that primarily wants the business of existing enterprises that are branching out, or maybe a certain type of startup that raises a lot of money before ever building anything. It’s frustrating and disheartening. My MVP is coming along, I plan on starting a small public trial soon, but I’m very concerned about the potential for this to derail me.

Anyone every build a company or product like this and run into these problems? Any advice, recommendations? I’d appreciate your help.