I have no experience with mongoose (glad they support our trails though!)
If you look at similar posts on other forums you'll be told to buy used at that price. Especially in a hard tail, you'll get a lot more bang for the buck in that price range. I would tend to agree with that recommendation
I used to sell Trek bikes in that price, it killed me. They almost always came back with taco rims and shifting issues that were hard to correct. Suspension forks in that range are typically terrible too.