The total cost of your project is largely dependent on your project goals and how much work you're willing to do for yourself. While you can certainly spend tens of thousands on outdoor, ISP-class equipment, you may find that you can save money (and get more satisfaction) building similar functionality yourself, from cheaper off-the-shelf hardware.
If you simply want to connect your laptop to someone else's 802.11b network, you'll need only a client card and driver software (at this point, compatible cards cost between $30 and $100). Like most equipment, the price typically goes up with added features, such as an external antenna connector, higher output power, a more sensitive radio, and the usual bells and whistles. Once you select a card, find out what the network settings are for the network you want to connect to and hop on. If you need more range, a small omnidirectional antenna (typically $50-$100) can significantly extend the roaming range of your laptop.
If you want to provide wireless network access to other people, you'll need an access point (AP). This has become something of a loaded term, and can refer to anything from a low-end "residential gateway" class box (about $100) to high-end, commercial quality, multi-radio equipment ($1000+). They are typically small, standalone boxes that contain at least one radio and another network connection (such as Ethernet or a dialup modem). For the rest of this book, we'll use the term "access point" (or the acronym AP) to refer to any device capable of providing network access to your wireless clients. As we'll see in Chapter 5, this can even be provided by a conventional PC router equipped with a wireless card.
While a radio and an access point can provide a simple short-range network, you will more than likely want to extend your coverage beyond what is possible out of the box. The most effective way of extending range is to use external antennas. Antennas come in a huge assortment of packages, from small omnidirectional tabletop antennas to large, mast-mounted parabolic dishes. There isn't one "right" antenna for every application; you'll need to choose the antenna that fits your needs (if you're trying to cover just a single building, you may not even need external antennas). Take a look at Chapter 6 for specific antenna descriptions.
Before you price a single piece of network equipment or visit a site, try to get an idea of exactly what you want to accomplish. Are you trying to add wireless access to a house that already has a cable modem connection to the Internet? Do you want to share a commercial DSL line with a neighbor across the street? Are you trying to connect several campus buildings together that already have an internal wired infrastructure?
It can be very helpful to draw an overview picture of your project before you worry about too many technical details. You can use programs such as Visio, XFig, or OmniGraffle to help you create a simple network diagram quickly, then fill in actual details as you accumulate them. How far apart are the potential sites? What sort of coverage do you need? Where does the Internet fit into the picture? Are there any obstacles in the path? How many apparent obstacles can be turned to your advantage? Remember that you can turn many hills that are "in the path" into high repeater sites with a bit of effort.
Once you have determined your goals, you can visit actual sites and start looking for the required gear.