Wireless ISP with airport ?

I have got Airport built into my Mac Mini at home. I would like to join an ISP and use the internet, however every 'wireless' ISP I've seen has to send you a modem or come round and install one. I don't need one I just need to join a service. I used to use internet for free from a hotspot next to my house. Since I moved I can no longer do this. I am prepared to pay the going rate (about £10-15 I think) for the internet but I don't see the piont in buying modems, paying installation charges, line rental etc. if I have a good wireless reciever in my computer. My Airport picks up a whole list of networks that require passwords how do I Join? Perhaps I've got the wrong idea?

The reason you could access that hotspot near your house was because the person there had a modem with wireless capabilities (and no password set for his/her network). If you want to use Airport on your Mac, you need to have something to provide the wireless capability. That is why your ISP needs to install the modem. You might be able to go to your computer store and buy the modem yourself. That will save you the rental charges for the equipment.

Thanks for your help, that makes sense! Perhaps you can help with my new problem. No phone line. All the ISPs I've seen (I've even found some with free modem) require you to have a BT landline to get wireless broadband. This does not make sense to me. I do not have a BT phone connection and can't afford to get one just to use the internet. I live on the 21st floor of a city centre tower block. I am recent mac convert and finding everything really easy with mac except getting online.
Thanks for your time.

You're welcome.

From what you say, it would be hard to get online whether on Mac, PC or Linux. You either need a phone line or cable line in order to get your internet access. The only alternative without those is if one of your neighbors had a wireless connection that you could "join" wirelessly. That, of course, would require your neighbor allowing you to share his/her connection.