Query regarding purchase of mhada flat

Sir/Madam, Good day I m looking forward to buy a flat in a newly built mhada building in mumbai from old tenant who got allotment just 3 months back, society is still not formed, He is in need of money so he is offering flat at very less price, but I have got information that mhada flat cannot be sold before 10 years. is it right? if yes than how could I go about purchasing flat legally and fullfilling all legal obligations, so that I m not harassed by mhada authority or old tenant in near future? please help