“What do you have to know to be a real estate salesman?”/” Lots.”

A popular real estate riddle is:
 
Q: What do you have to know to be a real estate salesman?
A: Lots.
 
The riddle has been cited in print since at least 1976. “What does an auctioneer need to know?”/“Lots” is a similar riddle.
 
   
Google Books
Biggest Riddle Book in the World, Part 2
By Joseph Rosenbloom
New York, NY: Sterling Publishing Company, Inc.
1976
Pg. 165:
What do you have to know to be a real estate salesman?
Lots.
 
5 July 1978, Xenia (OH) Daily Gazette, “Riddles,” The Western Star Countian Magazine, pg. 12, col. 3:
What do you have to know to be a real estate salesman?
Lots.
 
11 July 1980, The Daily News (Huntingdon, PA), “Riddles,” The Rayston Outlook, pg. 3, col. 1:
What do you have to know to be a real estate salesman?
Lots.
 
Google Groups: alt.humor.puns
“Puns of the Weak” 08-08-03
Stan Kegel
8/8/03
(...)
What do you have to know to be a real estate salesman?
Lots. (Kid’s Jokes)
 
Klosi Jokes
Category: Salesmen jokes
Date Added: 11/10/2007
Joke: What do you have to know to be a real estate salesman?Lots.
 
Twitter
Gary Unsworth
‏@TheHBNTips
What do you have to know to be a real estate salesman? Lots.
9:04 AM - 4 Oct 2015