Babysitting cat who is scared of out of the room time

I am currently babysitting a cat for my mom's niece and for the most part he spends time in my room because of the other cats and how they would get along is unkown. I would like to see if they were to get along, but first I want Nylan (thats the cat's name short) to get used to the house. He wants out of the room at times. So once we ensure the other cats are put away, we open the door to my room and he goes a little bit out, and then he chickens out and runs back in. We tried holding him till we got downstairs, but he would hide, and then run back upstairs to my room. We have had him now for a couple of week. I have tried to give him time, but would like to get him less scared so perhaps we can go to the next step. He is neutered and such a sweetheart. When we first got him he hid under my bed for a day and then started to wonder about. We could have him for up to a year at least so I would like to see if we can get all four cats to at least tolerate each other so he can at least have buddies with him while he awaits his owner to find a place where they both can be. So do you have any tips to help him get less scared?

Does he play at all? If he can start playing with a toy with you in "his" room, that might be a good distraction when he comes outside the room, and get him focussed and more confident! Particularly those "fishing pole" type toys can be very very tempting! Other than that, do you put things with the other cats' scent on them in his room from time to time, so he can get used to them?

Yeah we have a toy for him that I will use and as for the other cat scents before he came, they used the room at time so there should be stuff with their scent but I will get stuff for it too. Thanks for the advice. I don't want to start the introductions before we can conquer this.

Yup, play and "successful hunting" will help bring him out of his shell, and patience! :) I agree, you want him to be more secure before he interacts with the others, so they don't think of him as prey - "if I attack it will run away, how fun!"

You might also want to try feeding or giving treats to all of the cats at the same time in the same room. If you've ever watched the series "My Cat From Hell", the cat behaviorist has had owners do this with cats that didn't get along and it's worked out well. Good luck.:)