I know a ton of people will bash the low end bikes and they do it for a reason, you get what you pay for. You might be better off getting and older bike from Craigslist but since you said you have no experience with bikes you might end up with a bike that needs a lot of work. Do you know anyone that has some experience with bikes that could help you buy an older used bike?

I have twin boys and one has a nice Trek 1500 that he puts a lot of miles on and it is a great bike. I have an older Trek 2300 that I bought for $200 and had to replace the shifters/brakes for $250 so I ended up with $450 in an older but very nice bike.

My other son is a poor college student and he bought one of the Target Schwinn bikes, a Prelude I believe. He rides it a fair amount probably as much as you would or more, yes I had to do some work on it for him, tape the inside of the rims so he would not constantly get flats, do some adjusting of the brakes, shifters etc. but overall it has worked well for him. He bought it slightly use for $125.00 so I think he did ok for what he needed.