1. I will go with you if the plane fare is not too much
2. I will meet you there if I finish my work.
3. If I were you I would not ask for a raise now.
4. If you have a karaoke party, you will have to invite someone who can sing. Второй вариант: If you should have a karaoke party, you will have to invite someone who can sing.
5. If I were in their place, I wouldn`t be able to do such a thing to my parents.