@Mike Shahi they are apples and elephants. Flipping is a job, plain and simple. It is not an investment anymore than being a Realtor is an investment. It is a self-employed job.
Rentals are investing. Is it always passive? Heck no! Any investment without middle men will not be passive. You can get property managers and such to reduce that headache. I found with the units I manage that I started to dread checking email after a couple of years. The reason was I am super busy and the time it took to drive there and back (1.5 hours) and do the work was just too much, but I knew how much money was being saved so I felt obligated. I ended up making my time into fun math:
(Cost to have Contractor do it) / 2 = Fun money!
I do not have much discretionary income, so having full-on guilt-free screw off money made it worth it and I don't mind calls anymore. Maybe there is a simple root cause for you. Or maybe rentals are just not your flavor of "passive" and you can look into performing notes, lending, or something else, or maybe you just want to flip and build capital. Best of luck!