If your neighbor is willing to give it a good going over then I think that's half the battle.

From a safety standpoint, I don't think it's like the frame is going to suddenly implode or anything like that. It would mostly be inconvenient things like the chain dropping (falling off the gears) because a derailleur is out of adjustment. My son had the cranks (the arms that the pedals attach to) come loose on his Walmart bike. So if somebody who knows bikes checks it out then you should be OK.

At the kind of mileage your talking about the Walmart bike will probably do fine. You have to remember that some folks on this forum put thousands of miles on their bikes a year and ride in all kinds of weather. Having a component fail on you when you're miles from home when it's pouring rain or below 0 isn't something you really want to have happen.

I disagree with the poster that implies that buying a Trek vs. a Huffy is really about image and that it doesn't matter anyway since most people don't know the difference. This is a real difference in quality. But I also think that a big part of the difference in price is in the markup. Walmart can afford low margin products in a way that bike stores can't. So while there is a real difference in quality, you're paying a lot extra for the increased level of quality you're getting. That's why to me the real value is in buying used, but I understand that that is a risky proposition if you don't know much about bikes.