Is Rental Income Halal?
Quran’s Chapter 107 Verse 7 is an ethical attitude expected from God-fearing Muslims but is in no way a law in itself. The law in these matters only relate to ‘ لَا تَأْكُلُوا أَمْوَالَكُمْ بَيْنَكُمْ بِالْبَاطِلِ and of which riba is one of them. For example, in your first scenario, there is car that exists physically and can be returned to or taken back anytime, thus securing the principal and buyer has to only pay back for the principal amount for the car and rent for using that car until the period he materializes the ownership of the car. In case buyer fails to pay back, the car can be returned and seller is secure as far as a significant potion of his risk is involved and buyer will not be imposed with extra burden of recreating the principal (since car already exists). Hence, لَا تَأْكُلُوا أَمْوَالَكُمْ بَيْنَكُمْ بِالْبَاطِلِ doesn’t apply here. You can compare this with your second scenario and I think you will be able to appreciate the difference between two situations and why one is categorized as لَا تَأْكُلُوا أَمْوَالَكُمْ بَيْنَكُمْ بِالْبَاطِلِ and other is not.