When you sign up you choose whether you're here to buy or to sell. It's not a permanent decision — a buyer account can become a seller account any time from Profile > Start selling on Kosmos, and you keep everything: your orders, wishlist, messages and credit all come with you.
The two account types look different. A buyer account has Home, Browse, Assistant and Profile — no seller screens to wade past. A seller account adds a Sell tab for listings, drafts, offers and rentals, and an Earnings section.
A seller account opens straight away. You don't wait for anything to be approved before you can use Kosmos — you can browse, buy, and start building listings as drafts immediately.
Depending on how Kosmos is set up in your country, your listings may need your seller verification approved before they go public. If that applies to you, you'll see it clearly when you try to publish, and your drafts are saved in the meantime. Submitting your verification early is the fastest way through it.