What happens when a patent is filed for a single business idea or invention but there were multiple inventors involved in the effort?
Generally speaking, the answer is that the patent will be issued to all inventors jointly, assuming the patent application is filed properly.
Even if a single inventor was only involved with one of the claims made in the patent application, he or she is considered to be a joint inventor.
Mind you, being involved in developing the invention, as defined in the claims, doesn't mean that you can be listed on the patent application just because you followed the instructions of the main inventor. Patents are given to the people who provided the ideas behind an invention, not to the workers who followed their recipe to build the invention.
Similarly, the funders of an invention don't get credit for the invention. Just because you have the wherewithal to write a big check to an inventor, or employ an R&D staff that creates many patentable ideas, doesn't mean you can get patent credits for their work.
Needless to say, there is often considerable debate regarding who should be listed on an given patent application. At the end of the day, it's best to be honest about who contributed to the invention or the idea in a meaningful way that is consistent with the guidelines above. Put all of those individuals on the patent application.
You'll be following the rules and the spirit of the rules, and you'll avoid the possibility of expensive patent litigation later on, should any individuals claim that they were not listed as an inventor when they should have been.