Can you elaborate on the lineart/halftone combination you are trying to create?
Ultimately I expect you may have to ask your print provider about their printer’s specifics and if they actually can print with black alone and whether it makes a difference in pricing.
Thank for the reply. I'm working in Photoshop creating a black line images with white being the paper. I would love to use a a transparent gradient with half tone screens for the shading. I'm not sure whether the printer will see the images as true black and white or think the it is a image with gray tones (256 grays inks).
The print shop would usually create the halftone when RIPing the file.
That at being said... This sounds more artistic than technical. Work on a layered copy to apply the gradient as a separate layer, darken or multiply blend mode to preview. Trash the image layer, convert to grayscale mode. Then convert to bitmap mode using a halftone screen pattern, then combine over the original image.
Technically one could also combine the 1-bit line art with an underlying grayscale image in Indesign or Illustrator and export a pdf that combines bitmap and grayscale, but resolution considerations should be kept in mind.
For offset printing 1200ppi for 1bit bitmaps and 300ppi for CMYK- and grayscale-images are usually advisable but with print-on-demand I expect the digital printer may print at a lower resolution anyway.