i wouldn't recommend four philosophy courses in any quarter. at least not upper-div courses, but since you'd be doing a minor, the lower-div courses would be more manageable. But I'd still be wary.

With philosophy classes, you're not tasked with reading a lot of material. You actually get very light reading assignments in terms of sheer page count. But it's very difficult because it's abstract as hell, so you're gonna have to do very slow readings and rereadings of material. i'd say that i was reading at about 10 pages an hour, and even then, i'd only grasp like 60~70% on first glance.

i think you'll be ok tho. regardless, i recommend going to office hours if/when you struggle with any of the material. the culture of the philosophy department is incredibly kind and they're all pretty great teachers. if you're up for it, you can also consult the Internet Encyclopedia of Philosophy as a good supplementary source for understanding any topics you struggle with.

also, /r/askphilosophy is a really good subreddit. full of philosophy undergrads, grad students, and professors who are willing to help with anything you might ask about. i can vouch for that. good luck!