I've been freelance editing since I left my full-time job a year ago. Some has been with my old company, some with another company that contracts with some big publishers. I got the latter job because I found their help wanted ad on indeed.com, applied, and took their editing test. Everything is done electronically, communications are by email, payment goes directly to my bank account. Between that and giving private music lessons plus a few performing gigs here and there, I'm earning a bit over $1,000 a month.
I could be doing more editing if I wanted to, but I'm limiting it to 20 hours per week or less because I don't want to spend that much time on it. The teaching is more lucrative per hour than editing, plus I enjoy it a lot more, but I haven't tried very hard to find more students.