Buying a bike from the internet may save you money in the near term but it's going to cost you in the long run.
Someone I knew from High School, who recently moved to my town, reached to me about assembling some bikes for her and her daughter that she bought off the internet. We have some great greenway trails in the area and she wanted to ride them with her daughter. She purchased two bikes from an online retailer that I will not mention the name but you can probably figured it out for yourself.
The front wheel was indeed a nightmare. It was so out of true that the front brake was almost impossible to tighten enough to use it effectively. I got it to work with a minimal amount of rub. The rear was better but the shifting was off and I needed to tune it up, too.
The daughter's bike was little better but it was quirky. It had a 1 1/8 headset and a normal stem, with a cable disc brake up front and a V-Brake in the rear. The bottom bracket was tight and the cranks didn't spin without resistence.