Selling home way under value to a friend

Can someone sell their property that has not had a mortgage for many years to a friend way under market value? The property is worth over 1.5 million But the seller is open to selling to a friend for a much lower price because they just need to unload the property due to their age and having to maintain the property. What kind of things should they look out for as the seller and what should the buyer be aware of in this situation? 

Any advice is appreciated. 

Thanks!