Idioms

A CASH COW (= negocio de grandes ganancias)
Explanation of English Idiom #2
AN EASY WAY TO EARN MONEY REGULARLY.
Example of English Idiom #2
"INCOME TAX IS A REAL CASH COW FOR THE GOVERNMENT."

TURN YOUR BACK ON
Explanation of English Idiom #5
GIVE UP ON, OR ABANDON.
Example of English Idiom #5
"I NEED YOUR HELP BUT YOU JUST TURNED YOUR BACK ON ME."
(v.) = volver la espalda a, no hacer caso a, dar la espalda a.
Ex: We can choose to turn our backs on these principles with fatuous arguments which posit their anachronism and the nonexistent intelligence of computing machinery.

NOT CUT OUT FOR 
Explanation of English Idiom #6
NOT SUITABLE FOR SOMETHING.
Example of English Idiom #6
"HE TRIED MOUNTAIN CLIMBING BUT HE SIMPLY WAS NOT CUT OUT FOR IT."
(v.) = estar hecho para, ser lo de Uno, tener madera de.
Ex: If you consider eating out a couple times a week a necessity rather than a lark, you aren't cut out for living on a shoestring

SCRAPE THE BOTTOM OF THE BARREL
Explanation of English Idiom #7
THE VERY LAST, OR THE VERY WORST.
Example of English Idiom #7
"THESE ARE THE LAST VOLUNTEERS WE COULD FIND. WE REALLY HAD TO SCRAPE THE BOTTOM OF THE BARREL TO FIND THEM."

scrape + the bottom of the barrel

(v.) = estar en las últimas, tocar fondo.

Ex: Well, friends, we were really scraping the bottom of the barrel, and there was no joy, no joy at all. 

IN THE AIR 
Explanation of English Idiom #13
BEING DISCUSSED. GENERALLY OBVIOUS.
Example of English Idiom #13
"THE DAYS ARE GETTING LONGER AND THE FLOWERS ARE BLOOMING. SPRING IS IN THE AIR."