Lending 12 lakhs to real estatte

Hi I am Amit i need advise with regards to give money to one of Real estate for registration of a plot of land as they are broker and we have deal that when i give money of sum of Rs 12 lakhs in advance out of 18laks then they will arrange for registration for me with the actual owner Basically this real estate bought a big piece of land from some one and they are selling in plots to few individuals instalments, but they are asking me to give advance of sum of rs 12 lakhs well i will use stamp paper and will them by cheque, i have done the searching of land and found everything ok but i just need any more legal document can be done before i pay them by cheque thanks Amit