[Phantasm]

I use K, G, and F type stars for hunting down habitable worlds. A generous estimate is likely to be 50% of the stars have a planet in the habitable zone, with 50% of those planets being habitable without some form of terraforming.

That said, in my own space opera setting I have a habitable planet in each of those that has a stable zone (F types with orbiting white dwarfs - like Procyon - don't count) - and even those whose planets aren't habitable still get inhabited by humans in pressure domes. So even the M-types are inhabited, even if not inhabitable.

(A-types like Vega aren't likely to have habitable planets, due to being too young, if they have planets in the first place.)