Selling land to society develpoer

A developer wants to buy my land to make a housing society and suggests it on 50/50 basis..

I am new to this concept and would like to know what is the norm for such deals ?

Is there an advance payment involved ? How much will it be depending on worth of total land..

The developer wants to own half your land in return for spending money on developing the land. I think the point watch out for is what will happen if he does not fulfil his part of the contract? will you still own the land or will the developer have sold the land and disappeared with the money without undertaking any development.