I am a US resident, I work full time as an artist for hire, I am currently non-officially employed by the individuals I will be mentioning.
I work each month creating comic pages for a client alongside two other artists. This employment had no official contract other than any ordinary commissioned work under my TOS and I am paid using money they gain from their patreon. This however is not relevant in my question but may be of use?
These individuals contacted me with a new project, a calendar that they'd like to have done for 2016 for the comic. They've stated that they would like four images from me and will pay my own prices for them. They mentioned that they will be selling these calendars in digital and physical form. My dilemma is that I am unsure if I should be asking for royalties, or offering them the option to buy the rights to the images. I know it is well within my right to ask for these but I am unsure which route I should take on this. I don't know the right way to go about asking them about this or the amounts I should or could be asking for. Is this something I should just not bother with and risk the possibility of them making a large profit off of my work or should I play the business route?