Is it mandatory to enter into agreement for sale with every allottee? If yes, what is the maximum amount that can be taken without entering into agreement for sale?

The promoter cannot accept any sum more than ten percent of the cost of the apartment or plot or building as the case may be, as an advance payment or an application fee, from a person without first entering into a written agreement for sale with such person and register the agreement for sale under any law for the time being in force.