People saying that it is impossible are wrong, of course its not impossible. I am working to a cycle of 10 days per 3 Credits. For me to complete this, I dedicate 2-3 nights a week and generally one full weekend day/day off. I am awful with procrastination though so it's entirely possible to be much more efficient.
I first decided to go along this path at the very start of September. When I was researching what I wanted to do and how to go about it, I had it set in my mind that this would take a year, i'd then apply for 2019 entry to Uni. It was only when I got enrolled and started talking to people who had done the course that this was entirely achievable to make Sept 2018 entry to Uni. This however is based off a continuous 10 day cycle of going through modules I will be done by the end of May, but this doesn't include time off for Christmas/New Year etc.
When you look back at what you have taken on though, its quite a lot. At the start you need to be going through all of the introductory modules (which were very important for someone like me who had been out of academics for 15 years and had never written an essay) as well as tending to things like your personal statement. Make no mistake, the personal statement is a big deal and I have spent more time on that than any assignment so far. Its still not done. Along with this, I need to start working on LNAT revision as I need to take that for my Law applications. Yes, it's alot, but you just got to work at it.
One thing I will say though... I had the greatest intentions when I first signed up, "i'll work every night, dedicate my weekends" etc. After only a month, of my two days off, i've had to stop myself from working on one of those days otherwise I think I will go insane. Its important to keep a good healthy work/life balance. You saying that this will be your only commitment is great, but trust me, you will want some time off
In summary - If you want it, you can have it. Get signed up and get cracking on!
What are you thinking of doing, where are you considering applying for in ters of Uni?