Can you provide a demo video or the first still image of the video？

No, making a watermarked video means that all the video has been made. Providing the first frame of static image means that the video is 50% complete. If you are not satisfied, don't do it, it means we have done nothing. If you are afraid of the risk of paying too much, you can pay us to make a sketch for you (line draft, refer to the picture below). Sketches are additional work and are not deductible against the overall video production cost.