Billions, and you have to think your house is over 2.5tons (maybe) if average sized and if it has a basement about 8ft under think how hard it is to remove a post 2ft it 1ft in the ground so it don't think your house is going anywhere.
EVERYONE LiSTEN UP!ON THE NEWS LIKE 2 YEARS AGO PEOPLE BUILT A SMALL HOME WITH NOTHING IN IT AND IT WAS WOODEN AND THE GOT 6FT HIGH HELEUM BALLOONS AND TIME EM TO THE ROOF AND THE HOUSE LIFTED OFF THE GROUND INTO THE SKY!!!!THE END! (sorry for caps)
I did the math. An average house, without furniture weighs about 100,000 pounds (50 tons) and a party balloon can lift about 4.8 grams. If there are 453.59 grams in a pound, then it should take 9,449,792 balloons to make a house weightless. You would need more to make it go upward at a steady speed. You also have to take in the consideration that the balloons will lose their helium while you are filling them, so it would be impossible to full them yourself over a long time. Hope this helped.