I have spent some time around whitetail outfitters when I lived in West Central Illinois. I have never actually used one but I will give you what I have learned from interacting with them and some questions I would be asking if I was looking to hunt with one.
Whitetail outfitting is a broad term. Some places are full service and they provide you with meals, beds, transportation to and from the stand, help getting a deer out, etc. Other whitetail outfitters are just providing you with private land to access.
Are they going to have treestands up on that land for you already? If they do have treestands in place are you allowed to set your own if you choose or do you have to stay in theirs? If they have stands set for you will you be able to hunt different stand locations on that farm or on entirely different farms all together or will you be stuck in that same stand no matter what?
How many hunters does the outfitter have throughout a week, and throughout the season? If an outfitter has stands set up for you, every hunter that has been there during the season before you arrived has sat in that stand to.
What is the size limit? Most outfitters are going to have a minimum deer they want you to shoot. Depending on the outfitter it may be 130" it might be 160", it just depends. If you shoot a deer smaller then they want they will "fine" you. How much is that fine? Many outfitters it depends on the size. If their minimum is 130 and you shoot a 125" deer it might not be much, if there minimum is 160" and you shoot a 125" deer it might be a lot.
Try to find out about the atmosphere of the camp. Will it just be you and your buddy staying in a farmhouse or will there be 10 other guys who you don't know there too? Are those other guys first timers to this outfitter or have they been returning for 12 years, the same time every year. It is fun interacting with the other hunters, but some of them may not be there for the same reasons as you. They may want to stay up late, drink, socialize, etc. or they may want to be in bed right after supper to get up early the next day. There is nothing wrong with either atmosphere, but if you are expecting one atmosphere and get the other its going to be a long hunt. The outfitter sets the tone for the camp and how the guests behave.
I will think of more questions, but I would be very leary. I have met a lot of whitetail outfitters who are the scum of the earth trying to make a quick buck and I have met some who are salt of the earth do anything to make sure you are a happy client and return.