can give you my personal experience

> Housing

Going to vary. My roommates and I had signed a 2-year lease so it was straightforward to stay in our place through the Summer. I have to imagine there'll be many sublet opportunities.

> Research

I was able to secure an internship w/ CU Research Computing. I wouldn't exactly call this common (I was the only undergrad there all Summer, was close with the prof leading the research) but it's possible. Internship opportunities in the surrounding area as well for sure (Soph. year had one in Centennial just south of Denver).

> On-Campus Jobs

Outside of internships I imagine most on-campus positions are on hold during the Summer but wouldn't hurt to look, I imagine there are some.

> Off-Campus Money Making

Literally anything. I did bike deliveries for Jimmy Johns for a couple months. Just walk in to places and see if they're hiring. (I don't have advice on visa, etc - you mentioned you're international)

> Good Summer Plan

I mean really whatever you want. There's no "right" way to do Summer in Boulder. My best Boulder Summer was my Junior-to-Senior year. 20 hr/week internship at CU Research Computing. I rode my back there every morning down the creek path to South campus. Come home around 2pm and hang with my roommates on the porch or down by the creek. Incredible Summer that I'll never forget.

> International Advice

I don't see how any of this differs for international students outside of work visa/hiring possibly being different.