1.My house is one river apart his house. - My house is one river away from his house. 2. His house and my house are one river apart. - Perfect 3. His house is on the other side of the river/across the river. If I want to visit him, I have to take a ferry to get across the river. It takes me about 30 minutes to get across the river by ferry. - This is great. You could say other side of the river or across the river both would be correct. Good job!