Will the 2013 Medicare tax on real estate apply to all home sales?  No,  the new Medicare tax which is scheduled to go into effect on January 1, 2013, applies only to "high earners."   Home sellers whose adjusted gross income (AGI) is more than $200,000 for single taxpayers and $250,000 for married filers.   The AGI for married couples filing separately is $125,000.  The new 3.8% tax will apply to the "unearned" income of high income taxpayers.  Another 0.9% will apply to the "earned" income of  high earners. 

The $250,000/$500,000 exclusion on the sale of principal residence that has been around for some time is still in effect.   Any gain from the sale of a principal residence that is less than $250,000 (individual) or $500,000 (joint return) will continue to be excluded from income tax.

There are many provisions to this new law.   You should consult a consult a tax professional for specific situations.