Keep it simple.

In an effort to reduce flight training cost, some flight school come up with some money saving ideas.  Some of them seem simple and others are pretty complex.  Some of these money saving just wont work because they conflict with the regulations.  For example:

Fly your private pilot solo cross country to commercial requirements and it will count towards both the private and commercial requirements.  BAD IDEA!  Why? because according to the FAA legal department its not legal.  A pilot must fly a cross country for the private and then a second, longer, cross country while working towards the commercial.

Fly your long instrument cross country with a safety pilot.  Another bad idea.  The instrument rating regs state that this X-C must be with a CFI-Instrument (airplane or helicopter as appropriate).

Combine your commercial single and multi engine with one check ride.  Unfortunately,  this isn't allowed either.  Combined checkrides (other than the private and instrument) are not allowed by FAA legal and by policy. 

Those are some examples.  If someone comes up with an idea to save training time or money, question it and run it by your local FSDO and the DPE conducting the check ride.  You rally don't want to find out on check ride day you don't meet the requirements for the rating sought.

If it seems to good to be true, it usually is.  There's no free lunch, especially in aviation.