Most indie developers are not developing IP of interest to anyone other than the indie. Without marketing and continued development the IP is of little value.
Yes if you invent the next google in your spare time you could be in trouble. For this it’s best to get funding. At the lifestyle income level, your employer doesn’t have the time or money to waste on your passive income stream.
Obviously don’t be cavalier about it, but this will just get you fired not sued.
I have done OK on the Mac App Store, but I can tell you that selling two or three copies in 1 day is enough to make you top 5 in the Education Category.
I would add this advice: 1) start by working on your apps on the side while working another job, 2) while working said job, save and invest. Over time this can provide the cushion necessary to jump to full time indie.