The legal route is to send the builder a legal notice demanding either rent or the entire money you have put in. If there is no response then either the consumer forum or the RERA can be approached. Additionally, the NCLT is also a route. The NCLT route requires the presence of atleast 100 buyers or 10% of the total allottees.
Nevertheless, an FIR can also be filed against him before the Police and the EOW. Additionally, a letter can be written to the MCA to initiate SFIO inquiry.