My house has a 200 amp main panel, I already have a 100 amp subpanel to a detached garage, my question is can I add another subpanel to my upstairs, I have room in the main panel to add another breaker. I was thinking of installing another 100 amp subpanel for the upstairs as I may want to convert it to an apartment someday, the upstairs subpanel would be less than 8 feet from the mainpanel directly above it. Thanks in advance for any help

You can add as many panels and circuits as you like, however, someone needs to do a service rating load calculation to be sure the 200 amp service can handle the connected load.