May I ask how niche the directory website is?

With selling anything at all, it's about uncovering the need for the exact target market. So are you clear about what the value is to the client? What expensive problem are you solving for them that isn't already covered by local directory listings?

And do they see it as an expensive problem that they're willing to pay to solve?

If it's local retail business that you're targeting, it would be important to test the market with some face-to-face conversations. (In retail, from my experience, 20 minutes is about the maximum time to speak to the business owner, and it's important to get them at the right time of day. For example, a pizza shop owner is likely to have more free time in the morning, but a dry cleaner, in the early afternoon.)

It really comes down to the business problem that you're solving for them, and whether they are ready and willing to pay for that. Testing the waters first can save you from creating a great product with no one wanting to buy it, and I'd hate to see you go through that.

Are you selling advertising packages or placement packages? If you have product market fit, a process can easily be put in place.