This is the one of the model which propose because there might be some additional change made in the mid of the project that can result in the budget overrun and project delay. "Time and Material" approach is the best when our client want to start development instantly but has not created a project requirements documentation.

Suitable situation of the model

  The project specifications and requirements are change during the development phase.
  The chances of changes to the structure or architecture of the application during the development phase is very high.
   The duration of the project not to be accurately anticipated.

Pricing

  This is an effort based model with costs is being calculated using the following formula.

Total Project Cost($) = Allocated Resource * Rate(hourly/weekly/monthly)