500 meters, even 300 is much too far to be in usable range for WiFi. WiFi is designed to, in the best case, transmit throughout one small household. Also, physical barriers, like walls, cars, other buildings will severely degrade the signal. You might be able to get WiFi through one or maybe even two walls if you're lucky, but to get it 500 meters, you'd have to transmit at power higher than allowed by the standards bodies (and likely your government), and use an extremely directional antenna, with line of sight (no barriers in between).
The solution is probably to get your own Internet connection rather than trying to use theirs. You could also obtain a line of sight between your property and theirs (likely by building a small tower on your roof; check local regulations) and set up a very high frequency point to point link, but since you seem totally new to wireless communications, you (honestly) probably do not have the expertise to set one of these up even if you knew what you wanted, and would have to hire a contractor to design, spec out, price, and install a system for you, in which case you're better off going and asking an actual expert instead of asking us.
Lastly: the cost of custom designed radio communication systems like the ones I am talking about (which go above and beyond "WiFi") is often in the tens of thousands of dollars (or at least 7000 British pounds or so), not including labor. At that price, it is almost certainly cheaper (over a period of, say, 5 years) to pay for ADSL or cable Internet connectivity to where you live.