Here are some short word puzzles.
What's a not uncommon 7 letter word containing all 5 vowels and "s" and one other consonant (not necessarily in order)?
What's a common one syllable word, that when you add 1 letter to, becomes three syllables?
First answer
SEQUOIA - redwood tree
and another answer for 2
ORE -> OREO, thanks to the other answers for inspiration.
You did not ask for english words only, didn't you? So for the first:
oiseaux (birds in French)
The second could be seen on your face:
or not....
Looks like someone already got to number one, but the answer to number two could be
are +a = area
Another possible solution to (2):
Rode / Rodeo
Sure there are many possible solutions in a similar vein.