In your query you are using column alias in WHERE clause which is illegal in MYSQL.

Standard SQL disallows references to column aliases in a WHERE clause. This restriction is imposed because when the WHERE clause is evaluated, the column value may not yet have been determined. For example, the following query is illegal:

> SELECT id, COUNT(*) AS cnt FROM tbl_name   WHERE cnt > 0 GROUP BY id;

Above is taken from MYSQL documentation: MySQL docs

Correction in your query:

SELECT `L_ListingID`, `LA1_AgentID`, `L_Class`, `L_Class_`, `L_Address`, `L_City`, `L_State`, `L_Zip`, `L_AskingPrice`, `L_InputDate`, `L_Status`, `LM_Int1_1`, `LM_Int4_12`, `LM_Char10_12`, `LM_Char10_13`, `LM_Char10_14`, `LM_Char10_15` 
FROM `properties_residential` 
WHERE 1 AND ( LCASE(TRIM(`L_Address`)) LIKE '%kokomo, in' OR LCASE(TRIM(`L_City`)) LIKE '%kokomo, in' OR LCASE(TRIM(`L_Area`)) LIKE '%kokomo, in' OR LCASE(TRIM(`L_State`)) LIKE '%kokomo, in' OR LCASE(TRIM(`L_Zip`)) LIKE '%kokomo, in' OR LCASE(TRIM(`LM_Char10_12`)) LIKE '%kokomo, in' OR LCASE(TRIM(`LM_Char10_13`)) LIKE '%kokomo, in' OR LCASE(TRIM(`LM_Char10_14`)) LIKE '%kokomo, in' OR LCASE(TRIM(`LM_Char10_15`)) LIKE '%kokomo, in' OR CONCAT ( L_City, ', ', L_State ) LIKE '%kokomo, in%' OR CONCAT ( L_City, ' ', L_State ) LIKE '%kokomo, in%' ) 
UNION 
SELECT `L_ListingID`
, `LA1_AgentID`
, `L_Class`
, `L_Class_`
, `L_Address`
, `L_City`
, `L_State`
, `L_Zip`
, `L_AskingPrice`
, `L_InputDate`
, `L_Status`
, NULL AS `LM_Int1_1`
, NULL AS `LM_Int4_12`
, NULL AS `LM_Char10_12`
, NULL AS `LM_Char10_13`
, NULL AS `LM_Char10_14`
, NULL AS `LM_Char10_15` 
FROM `properties_commercial` 
WHERE 1 AND 
( 
LCASE(TRIM(`L_Address`)) LIKE '%kokomo, in' 
OR LCASE(TRIM(`L_City`)) LIKE '%kokomo, in' 
OR LCASE(TRIM(`L_Area`)) LIKE '%kokomo, in' 
OR LCASE(TRIM(`L_State`)) LIKE '%kokomo, in' 
OR LCASE(TRIM(`L_Zip`)) LIKE '%kokomo, in' 
--OR LCASE(TRIM(`LM_Char10_12`)) LIKE '%kokomo, in' 
--OR LCASE(TRIM(`LM_Char10_13`)) LIKE '%kokomo, in' 
--OR LCASE(TRIM(`LM_Char10_14`)) LIKE '%kokomo, in' 
--OR LCASE(TRIM(`LM_Char10_15`)) LIKE '%kokomo, in' 
OR CONCAT ( L_City, ', ', L_State ) LIKE '%kokomo, in%' 
OR CONCAT ( L_City, ' ', L_State ) LIKE '%kokomo, in%' ) 
ORDER BY `L_InputDate` 
DESC LIMIT 6

In above query, The commented part is not required since the columns are itself NULL. So you can remove commented part from WHERE clause to make your query correct.