I work a full time day job and moonlight on the side (ecommerce selling proprietary products to be more specific) - and plan to continue to do so.
I disagree with "taking the plunge or going all in approach". You stated an apartment so maybe you don't have to much to loose. But for me by the time I started my company I was 31 married with a newborn, amazing acreage, couple cars (I am a car guy!)... An outsider would say living the American dream.
Now I have been in business for 1.5yrs have a second child
I wake up about 6am. get myself and one of the kids ready quick breakfast, and typically leaves me with 30min to take care of emails or get a last minute order out. Work 7:30/8-5. Spend time with family till atleast 8pm. Then depending on the workload I spend between 30minutes to a couple hrs working on the business. Most nights fullilling orders answering emails I didn't get to on my breaks etc- but some nights programing, marketing, new product development...
One big item I do - If I think of something during the day that I want to do or look into I write it down(aka save it on a list in my phone). I slowly pick away at that list each and every week.
I do take lunches early/late to make business calls sometimes but don't let my moonlighting affect my overall job performance.
Now if I had worked full time on this - my income may have surpassed what I make at the 8-5 but I wasn't willing to take the risk and loose all the equity and quality of life I had already created.