You can only assign them to one business at the moment. What you are asking has been suggested and requested a few times, though!
For now though: hire a part-time cleaner. If you hire full-time, they will demand at least 30 hours a week. If you hire part-time, they only require 10 hours. If you are open 7 days a week and assign them 2 hours a day, they shouldn’t resign.
Correct - that’s another feature that has been requested: maybe HR could have more refined searching or something in the future!
For now, though, it feels like a pretty even split between full-time and part-time, but of course, the way random numbers work, you might have to put the number of candidates to search for up to 3 or 4 to get the one part-time.