Which is correct:
1-How much money do we need for buying that car?
2-How much money do we need to buy that car?
In standard BrE, I wouldn't expect to hear #1; #2 would be the usual form.
(It would be difficult to call #1 "incorrect", in BrE; but you might call it "not used" or "unidiomatic".)
Not a professional ESL teacher.