Time and Material (T&M), also called pay-as-you-go, works best if you want to start the implementation of complex and long-term projects immediately. This model recommends insufficient insight into the end product for forward-thinking projects projected to expand and grow. The significant advantage of the T&M model is adaptability and flexibility, as you can customize your demands and still pay just for the amount of time a development team puts into work on the project. The workflow is divided into sprints and after each of them, you can evaluate the progress and modify the initial project assumptions. With this contract, the invoice is based on pre-set hourly rates of each team member. The total project price is defined by your product's time and resources (hardware, dedicated licenses, etc). When it comes to management, you will be involved in iterations and constantly engaged in the entire process. Therefore the appropriate knowledge to verify the quality of the sprints and their results is required.
To enhance the original concept, you can modify it along the process.
The customer does not need extensive pre-planning to evaluate all the hazards, modifications, timeframes, and challenges.
The customer could easily step in to determine how the developers are handling the process or propose a change.