Question:
May money from the sale of a sefer Torah be used to make another sefer Torah kosher (being that them money is not paying for Torah directly, but for service)?
In an extremely poor community lacking a mikvah with none remotely nearby, could Torah be sold to pay for mikvah?
Answer:
A kosher Sefer Torah may not be sold in order to raise money to fix another presently non kosher Sefer Torah. If the Sefer Torah was already sold, or it itself is a non kosher Torah [very common with old worn out Sefarim, could be verified by a sofer] the money can be used for fixing a Sefer Torah.
If no other resources are available, a Sefer Torah may be sold to build a mikvah.
Sources:
Shulchan Aruch Y:D 270:1, Shach ibid. 3, Taz O:C 153:1, Magen Avraham ibid. 4, Beis Yosef O:C 153.
Igros Moshe O:C 1:51 [selling Torah for Mikvah]
