I should take offense at that, just like all other trainers should...but it was funny so I won't.
Training is very time consuming, can be very frustrating depending on the client, and is fine to do part time but you're always working around someone else's hours...so you typically work when other people aren't, if you get my meaning.
Good stuff is when you have a client who reaches their goals, feels better, buys you stuff (woo hoo!) and devloping a close trusting relationship with them. As a trainer, your job is to safely monitor the progress and general health of your clients and help them to get whereever they want to be. Some tips though (from someone with 3 years experience, which isn't really much, so take it for what it's worth).
1) Don't be afraid to say "I don't know." If you don't know the answer to something, then admit it and try to find the answer. A good trainer will not necessarily know everything about everything, but they will know where to find it if they need to. It is a continual learning process. Don't EVER assume you know everything.
2) Every person is an individual. What works for one probably won't work as well for another. Don't adhere to one methodology all the time.
3) Be safe and courteous in everything you do, espeically if you have to tell a client they can't or shouldn't do something.
4) Always explain WHY they are doing something. Too many trainers know what to do, but can't tell you why you should do it. Focus on that and you'll be better off.
As for financial rewards, it takes a long time to build up clients so you are making good money. At the gym I'm training at right now I get $30 an hour and then it goes to $40 when they are with me longer than ten sessions. So ten hours a week = $300/week...not bad, but it takes a while to get there.
Hope it helps.