Would you share your wireless network with neighbors?

[VeloVT]

The duplex I live in was recently sold. The new owners (my new landlords, who will be living in the upstairs unit) noticed that they get our wireless network signal and asked if we would be willing to share it (provide them with the password, and then they would split the cost of our cable internet).

They are a nice young couple; I trust that they have no ill intent, and further, it's my impression that they aren't necessarily terribly tech savvy.

At first, because I basically trust them, I was comfortable with this. (I don't have any moral issues with depriving the cable company of an additional account, hope you won't judge me for this!). However, as I was getting ready to share the password, I started getting cold feet. I have my laptop's firewall enabled and all sharing disabled, and all files that are sensitive on an encrypted disk image, so it should be relatively safe, but it still makes me anxious. We'd be sharing our network not only with them, but also any house guests with whom they share our password. If you accidentally clicked on a machine on a local network, and discovered you could access some files/applications/services, even if you had no ill intent, is it possible you might click around just out of curiosity? I think so... Also, what about passwords and the security of other information transmitted over the network? This is really a hypothetical concern as I am 99.999% sure they have neither the inclination nor technical skill to do anything sketchy, but still...

I have considered getting a new AirPort, as the newer models allow you to set up guest networks. The new device would have benefits to us other than just allowing us to share the network more securely - mine is quite old, probably seven years old, and while it works fine, it has fewer features and probably less range than the newer models. I'd rather not spend the money, but I am open to it - it won't break the bank.

What would you do? Especially those who are more on the computer nerdy side, would you have concerns about sharing your network in this way?