Changing just one letter at a time, you can go from fuck to hole, and every word in between is pretty hot in itself:

FUCK
BUCK
BUNK
BUNS
BUDS
BODS
BOYS
TOYS
TOPS
HOPS
HOPE
HOLE

From the hole we can follow our way to lust:

POLE
POSE
NOSE
NOSH
GOSH
GUSH
BUSH
BUST
LUST