Some people do work full-time and do a graduate degree full-time. I was never one of those people, but I wouldn’t recommend it. A full-time graduate degree - especially one like an MFA in professional writing - requires attention and some immersion aspects to it; it’s better to do it if you can either devote your energies to it almost fully (working part-time would be fine) or if you can complete it part-time. If you really can take 2 classes a semester, then that might be doable - but that depends a lot on you.
Also, are you sure you need an MFA in professional writing to be an editor?