Well, are you going to build hotspots or become a WISP? Big difference. WISP's provide Internet access like a dsl or cable provider. Hotspot providers might use DSL or something as the backhaul.
You can flash the Linksys Wap11 to use NoCat Splash to force a start page. The problem is that it is in RAM, so as soon as it gets unplugged (which you need to do on occassion to reboot it), you lose the Splash page.
But, you can use a crappy PC (A 486 will do) and put NoCat on it with some Linksys consumer equipment and have a pretty inexpensive hotspot. Maybe use Yahoo! Stores or something for the https so you can take credit cards and have them handle those transactions (Though it costs about $100 a month).
I *really* like Linksys equipment for an inexpensive HotSpot. If you have just a few more bucks to spend, you can get some Zyxel equipment for the Hotspot, which has a built-in radius server. Gotta love that.
Now if you're talking a true WISP, most of this is moot.
