See 5 apartments for rent under $900 in O'Fallon, MO. On ForRent.com, we're here to help you find a home that fits your budget without sacrificing your apartment must-haves. As you explore O'Fallon apartments under $900, remember to consider the amenities and location that matter most to you. This will ensure you find a place that's not only budget-friendly but also perfectly suited to your lifestyle. Start your apartment search and take the first step towards finding your new home today.