IoT systems are complex and heterogeneous, and consequently difficult to control and secure. This problem is compounded by the fact that the devices are often inexpensive with little computing power. In this paper, we present our experience within the Safe Place project which aimed to create an IoT system for healthier living environments, motivated by the SARS-Cov-2 emergency. The implemented IoT system can monitor people's movements, check the healthiness of the air, sanitize spaces and objects, and provide support to isolated people. Our recipe for a cost-effective secure IoT system trades-off security, usability, and cost, and is easily repeatable and implementable for other similar IoT systems.