You're describing the problem, it's setting, and your platform very vaguely. But from general principles, it's best to charge in the least noticeable way possible, so a % of the seller's commission would be the best method.

That way it's invisible until a sale comes through, and even then, it occurs automatically as a deduction. If you charge a subscription fee you're requiring the seller to actively pull out their card and send you money, a barrier that's much harder to get them to cross than the less noticeable, passive and automatic deduction from a sale.

If you'd like to discuss the issue with respect to the specifics of your particular platform and its market, let me know and we can set up a call,

best,

Lee

Having consulted across different industries I realized that, like it or not, every industry has a preferred behaviour around establishing partnerships and often those behaviours reflect customer behaviour. I don't have the specific data for your sector but that's where I would suggest you start: what do the most successful do? Choose better places? Are better marketers? Build better relationships? Then look to the opposite end and see what the least successful do? And what does everyone in the middle does? I'm a decision making expert and wont know specifics about your field. But I do know that most of the poor decisions are made because we solve the wrong problem. So, I'm going to take a leap of faith and suggest that its not the pricing model you should focus on. I'm not trying to be misterious but I would need a lot more information from you to suggest the next step. For now I hope I got you thinking about doing some market research first. No point rushing with the pricing model. Even if you choose something that succeeds short term, it wont last. At least in most situations. You can call me for follow up questions. Good luck!

The best way to determine this is by asking your agents directly. Interview them (either via a survey tool or on the phone) and determine which method THEY would prefer and what THEY would pay for that value (in both scenarios). This will let your decisions be driven by data, while providing you the opportunity to be more precise with your pricing scenarios.