1. What do the following words have in common?

CUR
FUR
COP
SPUR

2. What do the following words have in common?

MONEY
FRIDAY
CANNON

Answers:

1. Each word can be followed by IOUS to make a new word:

CURIOUS
FURIOUS
COPIOUS
SPURIOUS

2. Each of the three words can be preceded by (near) synonyms to form common phrases:

EASY MONEY
CASUAL FRIDAY
LOOSE CANON

Credit:
#2: Jennifer Nutt