What is Guaranteed Maximum Price contract?

[Good-Person]

There may come a time when the builder may have a limited budget. In such kind of cases, the builder may form a guaranteed maximum price contract. This means that a contractor may have the ability to set a specific kind of budget for the builder. However, the price of construction must not exceed the maximum budget. So, it is understandable why many contractors may avoid this contract. So, is it really that common?