You introduce one legal association — and it has 400 large law-firm members. Each firm gets a free corporate account, and each firm then invites every client it serves: businesses and individuals alike. One handshake at the top cascades into hundreds of firms and the entire client base beneath them. You hold the inviter position above the whole tree.
Law firms have something almost no one else does: a trusted, ongoing relationship with both businesses and people, and a reason to keep them close. Give each firm a free corporate account and they have every incentive to bring their clients onto a verified platform. The association is the corporate account earning 10%; you, the inviter who opened the door, earn 5% of every business subscription anywhere in that cascade — the firms, their business clients, and the businesses their individual clients bring.