Is a Baal Koreh permitted to receive payment for laining? Why? Sources?

There are two basic questions over here: A. Is it permitted to receive payment for the actual reading of the Torah even during the week? B. Is it permitted to receive payment for reading the Torah on Shabbat as our Sages prohibited receiving payment for jobs that were done on Shabbat? In regard to the first question about receiving payment for the actual reading of the Torah even during the week, it would seem to be forbidden because the reading of the Sefer Torah in public is fundamentally a Mitzvah of Talmud Torah, and it is forbidden to be paid for teaching Torah as the Gemara in Nedarim 37. says “ just as I [taught] for free so should you [teach] for free”. Nevertheless it is permitted because the Baal Kore is not getting paid for the Torah learning, but for the cantillation notes and tunes that are defined as a trade and art. Another reason can be said that he is not getting paid for the Torah learning but for the time that he spends preparing the reading of the Torah and the reading itself, as stated in the Ran in the name of the Yerushalmi and in the Tosfot regarding one who teaches Torah. During this time he cannot work to earn money. This is called “Sechar Batalah”. In Sefer Mikra’ei Kodesh he determines that it is preferable that the Baal Kore be paid in order for the community to be sure that he will always be prepared and ready in Shul on time for the Torah reading due to him being a paid employee. And indeed it is the custom that a Baal Kore can receive payment. In regard to the second question whether it is permitted to receive payment for the reading on Shabbat, there is a disagreement among the Poskim whether our Sages prohibited payment for jobs that were done on Shabbat also regarding something that is a Mitzvah. However even according to the lenient opinion, he will not see a sign of blessing from the payment he will receive; therefore it is commendable for the Baal Kore to take the payment Behavlaa [Included together] with the payment for the weekday reading or for preparing the reading during the week. [מאמר "בעל קורא בשכר" של הרב מרדכי פוגלמן מקרית מוצקין פורסם בירחון "בית הכנסת" של בית הכנסת הגדול בתל-אביב, אייר תש"ז, עמ' 11, ר"ן בשם ירושלמי נדרים לז. ד"ה ולענין הלכה, תוספות בכורות כט. ד"ה מה אני בחנם, ספר מקראי קדש להרב יעקב יצחק יוטעס, לעמבערג תרכ"ד, שער שלישי סעיף ב ס"ק ג, שו"ע או"ח סימן שו סעיף ה וסימן תקפה סעיף ה ובמ"ב שם, שערי אפרים שער ג סעיף ה, שמירת שבת כהלכתה פרק כח סעיפים מח, סא, סו].