If you plan to prepare a project for printing, go straight to CMYK mode and calibrate your color as the first step.
Color correction should be the first step since you might need to
choose the layout's Pantones or CMYK colors that fit with or is from
Usually in the printing industry, this is the first step because all the material is prepared first by the "color management" team and then sent to the designers. Then some adjustments can be done again but they are usually minor. The same process is logical for freelance designers.
If you calibrate your colors at the end, you could 1) forget to do it or 2) have mismatch in your layout and then have to change your CMYK recipes in it it (or them) (eg. InDesign, Illustrator, etc.) It's efficient to do it as first step and then build your layout on a solid foundation!
If you received quality pictures from a photographer or bought stock pictures, the images are usually already well calibrated in RGB and they don't require a lot of adjustments if this step was well done.