If your loan proceeds will be used to construct the home, then you need to follow the Flood requirements.
If your loan proceeds are only to purchase the land, then you do not have a covered loan.
You could pull one now, but if they are going to get a loan later to build the house, you must pull a SFHDF then. If they are not going to get a loan to build the house, your bare land loan will have a building (eventually). When that happens, you would need to pull a SFHDF.
Pulling one now might be a good customer service issue too. You could inform them that their property has a high risk area, but it's not required and I don't think you should/could pass on the fee to them.