Pricing of work? By hour or by images produced?

I need some help from the real pros of which I am not.

In an attempt to help a family member I seem to have become involved with a photographic project. I am now being asked to provide an hourly rate, the catch being that the requester does not really know what they want. The task involves outdoor city/architecture/landscape shots for a website promoting the location.

Should I quote an hourly rate or encourage them to base my compensation on a fee for the work I submit?

This is just a hobby for me and while I don't mind getting paid I would like to make sure that this is fair for everyone.

Thanks for any advice, sorry for being vague as I am a bit suprised at how this has grown.
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