I have done a huge amount of research on property in Bucharest. And to be honest the rental yields are very good. Providing you put the work into your research, it has probably been the best place to invest over the last 5 years in Europe and for me still number one if i was to invest in Europe in bricks and mortar.
I have a few friends living in Bucharest city and the rent is indeed pretty high. There is a huge difference between Bucharest and the rest of Romania. It's like comparing London with the poorer city in England. The law of averages would not be a good research tool here, each district should be viewed as a separate entity, then a true reflection can be made.
But i still think Cannes is a great investment, but i would be surprised if it didn't cover the mortgage ? The rental demand is so strong that property prices will remain strong. It wasn't so long ago that a studio in Croisette in Cannes were €80,000 and less.