1. I am looking for a big house which I can live in.

2. I am looking for a big house to live in.

3. I am looking for a big house which to live in.

4. I am looking for a big house in which to live.

(Sentence 1 is a complex sentence. The others are simple sentences. Are all the sentences grammatical and do they have the same meaning?)

2 answers

1 is awkward ~~> I am looking for a big house in which to live.

2 is fine.

3 is incorrect; see #1.

4 is fine; see #1.

Complex sentences = 1 and 4.
Simple sentence = 2.
Incorrect = 3.
Try not to end sentences with prepositions, which are designed to relate to objects ("live in" what?).

I hope this helps a little more. Thanks for asking.