Honestly, for $100 or less, I don't know if you can go "wrong". I don't know anything about this one, I do enjoy air rifles A LOT though, so I would highly suggest you type in Crosman MK 177 in Google or on YouTube and check out the reviews. I saw that YT had a couple of videos that might be informative. I looked on Cabelas and it only had 3 reviews, but they were all 5 star. Check with retailers who sell it and look at reviews from buyers. Those are usually pretty honest. Sometimes, heck, often times, it's the best you can do and most of the time, it turns out to be enough. At least you can make an informed choice and have half an idea of what you're getting into. Oh, and Air Gun Depot has one for $79.99, same price on Amazon with free shipping. Good Luck!
Since you only mentioned hunting, try to stay close to 900+ fps in 177 or 700+ fps in 22. A 22 pellet lets you shoot a little farther away with better retained energy than a 177. I'm afraid you won't be getting much of a squirrel killer spending less than $100. My suggestion would be a Gamo Silent Cat for around $150 from Walmart. As others said, spend time with Google, WalMart, Amazon and Pyramyd Air.