Mongoose builds some "ok" bikes for a beginner and if you don't plan on doing alot of hard trail riding. I have 2 nephews that have Xmart mongooses and they are holding up relatively well, especially if you consider the cost. I am not an advocate of buying these types of bikes, but if it helps to get another person in the sport, I say go for it. If you decide you like cycling and want to continue, you can always upgrade to a better steed later. I would check around though, some models are better than others, and have better spec'd components.

Good Luck and welcome to the forums....(ha... the first time I got to say that before someone else)