Ticketing is a large part of it, but there is so much more involved than that. Actually many agents are moving away from the old processes of ticketing - GDS systems are just too expensive and they aren't as useful as they used to be.
You do however have to be extremely familiar with your geography, so that you know where you're sending people even if they don't (So, you want a rental car for Hawaii so you can visit the other islands huh?). The ins and outs of various cruises and tours and the legal requirements and consequences of each, insurance and what it will and will not cover and why you should have it, etc. A good portion of the industry still is in WHO you know, so it can take a while to build up those contacts. For instance I just referred a client of mine to another agent (gasp!) because I know her and she's better able to handle his needs for this particular situation. If you have clients wanting to take an eco tour of Costa Rico and you don't know which of the tour companies to pick, then it helps to know someone who's had experience in that area that you can call and ask for advice.
And I'm going to say the same thing here that I've said elsewhere about being a
travel agent - it doesn't earn a whole lot of money. I would have made more money last year working at McDonalds. If you're working just on commission then you have to be aware that most airlines don't pay commission any more, about 1/3 of the time the hotels you're booking won't pay you the commission, and about 1/2 the time the car rental agencies won't pay the commission. Part of my job in the last agency I worked for was researching pending commissions, and it took a fair chunk of time.
It's also a BIG commitment, because although you might only intend to be in it part-time you have to be prepared for the fact that if something comes up that requires immediate attention, you need to deal with it until it's done. And that can mean sitting on the phone all day trying to get through to vendors and airlines to get a problem straightened out for a stranded client, or trying to get that cruise cabin booked before the sale is over or other such things. And if you happen to have plans, well too bad. This is not an industry where you can put things off until tomorrow. It's a "you snooze, you lose" industry.