Open Question: We are looking to buy our first home. So the questions I have are:?

Is it more expensive to buy a land and build a house on it or is it expensive to buy an already built up house? Is it ok to buy a house which is built in 60's? I liked a house which has been upgraded but was built on 64, but it has really low ceiling made of Composition Shingle. Is there a way we could increase the ceiling height? How much would it approx cost? The built up area is 1540. It has two adjoining rooms which are small, and so we would want to break the wall between them to make it bigger, does that costs a lot? I know I can ask these questions to a contractor but just wanted to get an idea beforehand if any of you knew abt this? Thanks Thanks