Foreign Language Workload?

I’m a linguistics major with emphasis in East Asian Languages and Cultures (Modern Chinese track) In addition to taking Chinese classes (which are 5 units for the first 2 years).
I’m planning on taking either Spanish or Russian to satisfy my second language requirement of my major. I noticed that Spanish classes are all 4 units whereas intro Russian classes are 5.
How much work do foreign languages classes actually require in comparison to, say, an anthropology or chemistry class? And what is the nature of the work? Also, is there a significant difference between lower div classes and upper divs in terms of workload? Thanks!