Do real estate agents get paid a base salary on top of commission of is it just commission only?

Generally speaking, agents get paid on commission. The person saying 6% is only partially right when it comes to commission. Sure, the agreement for selling your home may be 6$ but generally that is split between a buyers and sellers agent, so let's say the agent gets 3% of that. Then, they have to pay a set percentage or amount to the broker that holds their license and sometimes even their company in general. So rarely does a real estate agent get the full 6% even if they act as both buyers and sellers agent, because they still have to pay the broker.

In some cases, they can be paid in a different fashion. Everything from salaried to part salary/part commission. However, it seems as if this is less common.

from my experience it is commission only because real estate agencies have no other income. how could they have other money?

Commission only. The commission you receive is negotiated between you and your principal broker. Then you have to split this between you and your office.