I babysit for a LOT of different families, for kids of all ages, and I too have had my share of 4-year-olds. When you get there, just to make sure he doesn't freak out when his parents leave, I'd suggest asking him to show you his room, or his toys. After that you can move on to playing with his toys or another game.
Game ideas:
-Hide and go seek (I think it was mentioned before, but it's really important: set boundaries for him so he doesn't hide somewhere you wouldn't think to look. I usually choose 2 floors and they have to stay on them. If they don't, they're "it" next).
-Tag
-Candyland, Chutes and Ladders (my 4yos LOVE playing them)
-Coloring
-Playing "house" or "school".....kids always love playing the parent or teacher!
When all else fails, use a movie. I almost always ask them to pick out a movie, cuz it gives all of us some downtime. Make sure it's not too long to finish, cuz otherwise you'll have a tough time getting them to bed!
Make sure you ask the parents for any bedtime routines they might have. Sometimes kids have things done a certain way. Right before bed, you can give him a snack, but don't give him too much sugar, or he will not be going to bed anytime soon. If he struggles at bedtime, make a game of it. Tell him you'll time him and see how fast he can do it, and the reward is a story. Or pretend it's a journey, and the destination is his bed. I'd definitely suggest reading him a story before he goes to sleep. It really calms kids down. When you're done, make sure you ask him if he wants the door open/closed/half open etc., and if he has a nightlight or anything. The parents might tell you that beforehand, but it never hurts to ask again. If the kid asks you to stay with him "until my parents get home" (which HAS happened to me, haha), then just sit on the floor of his room, silent, until he falls asleep. Then you can go downstairs. Oh, and one more thing: Definitely try to leave the house the way you found it. Clean up dirty dishes in the kitchen, wipe off the table and counters, and if you didn't have the kid help you before bedtime, clean up any toys that were gotten out. Then, if you have the time after that, lol, you can finally watch some TV till the parents get home!
As for payment, when I got my first babysitting gig, I just told them to pay what they felt was right (which was $6 an hour). Now, when I get a new family, I tell them that I usually make $6-$10 an hour, and they can just pay what they feel is right. When you don't set a rate, you usually make more.
Good Luck! It sounds a lot hard than it is, trust me.
