There are various companies  which sell  ‘money earning schemes or
plans’  in the  internet  for  example   www.sixfigureincome.com    
company,  I  want  to know  that  all  those  companies  which  are 
selling  money earning  schemes  or  plans  in the  internet  are 
doing   ‘legal  businesses’  in  the  internet  or  those  companies  
are   ‘frauds’   so  that  I shall  be able  to  purchase  the 
products  of  the  above   mentioned   companies  if   those 
companies  are  doing  legal   businesses?

My opinion and two cents worth is as follows:
Dont waste your time, most of them are a "virtual" rip-off.

It is quite possible that all of these companies are legitimate in
their doings.That does not necessarily mean that they are not
frauds.For example,If I tell you that you can make double what you are
making now,that does'nt mean you willOn the other hand it's not false
advertising because you could take a bankrupt homeless guy off the
street and he'd definitly make double.So as you can see the tricks of
the trade are easy to pull off without breaking the law and many major
companies are capable of such.

Some companies could be legal and still be frauds.If they say you can
double your income,that doesn't mean you will.Some people would double
their income .You could go to any of these companies and they are
probably legal but it is usually a huge mistake to have any dealings
with them