If you're thinking about buying a budget bike, it's important to remember that these aren't "cheap" bikes. They are simply made with quality construction and parts, for a lower price. You get what you pay for in a sense. Budget Bikes are not inferior bikes, but they won't have the high tech gizmos and accessories found on higher-end bikes.
The key to getting a good bike is to be aware of what price ranges you're looking in. If you're just starting out and haven't quite found your niche yet, then going with a budget bike is a great place to start. You'll know what you're getting into and you'll have more control over how much you spend since you aren't overpaying.
A good starting point is Craigslist. There are listings for almost every kind of bike. If you have a serious passion for biking, then this is the perfect outlet for you. Many people who are looking to get into the sport on a budget also fall into this category and are willing to sell their old bike. You'll often find really good deals on these listings.
Another great place to check is online auction sites like eBay. These are an excellent source for bargains and if you have time, you can even buy your bike there. Just be sure that you keep an eye out for these kinds of deals because many times there are fake bikes being sold. You'll want to go with a reliable seller and you'll have to be on the ball when it comes to making payments and delivery dates. There is some risk involved with buying anything on the internet, but if you plan to stick around and don't mind a few bumps and bruises, then eBay is a great place for you to start.
Don't rule out Craigslist as a secondary buying source, though. It's still a great place to find a deal on a bike, but you won't be dealing with a seller or buyer face to face. However, you should still use common sense and try to protect yourself by always checking the background of any seller you're thinking about buying from. If you do your homework, you'll be able to avoid unscrupulous individuals.
The final place you might look are local classified ads. This can be a good place to find a good deal, but only if you know what you're looking for. Classifieds will usually contain bikes for sale by owners and you can peruse the offerings and select the one that appeals to you. You'll need to do your homework in order to determine the quality of the bike to be sure that you're getting a good deal.
In summary, you have a lot of options when it comes to buying a new bike for a budget. Make sure to do your research and take your time. Stick to trusted sources and don't give up. You won't get your money back, but at least you won't be wasting time. Once you've found the right bike, you'll be ready to enjoy hours of great riding!