Here's a little bit of info that I can share.
We put up a small ticketing office as a sideline before.
We only sold tickets from 1 airline because we knew the owners.
Basically, they had to train us in using the ticketing software that they used, and they hooked our computer into their system so we can book flights.
It was operated with just 1 person, 1 computer.
We didn't operate that long because to make it viable, we needed to sell tickets from other airlines, but we didn't have the time to do it.