Contract Law: What happens when the contractor backs out?

So, we have Rohan, a young entrepreneur, who hires his friend, Tanmay, to build a house for him for ₹10 lakhs. Tanmay is supposed to start the work within a month, but he's now saying he can't do it due to some unforeseen problems. The agreed-upon completion date has passed, and Rohan has paid Tanmay ₹5 lakhs as an advance. Tanmay is now refusing to complete the work and return the advance amount. Rohan is all upset and wants to know what he can do. What legal remedy applies in this situation? Should Rohan sue Tanmay for breach of contract or something else?