Legal agreement b/n builder and owner

Respect sir,
I am planning to construct a new house in my land located in urban area.we all patients suffering from peralisis so we decided to give entire construction to a registered builder.
So kindly tell me what points included in legal agreement between builder and owner.
Kindly give information if he not
construct building according to the agreement what action we can take against him legally.
Why because we all patients we can not fight with builder thats why kindly give detailed information regarding the above

Thanks a lot