Only flip 1 or 2 bikes a year, if even. I won't mess with bikes that are a basket case, unless it's a labor of love.
The flips I still do are either a free bike that I know will sell easily or a high-end bike in good shape, purchased at a very low price. If I can't clear $50/hour for my time, I won't touch it.
I'll only do the minimum to make them clean, safe, and functional. Full disclosure of any issues to the buyer. I try not to spend more than 2 hours on the whole process.