You must first understand that there are laws concerning a non-Jew performing work for a Jew on the Sabbath. Generally, it cannot be done. See this quotation from Aish.com:
My husband and I are Christians and our neighbors are Orthodox Jewish. Sometimes on any given Saturday, our neighbors knock on our door and ask us to turn on the air conditioning, etc. We've always helped them out, not understanding the full reasoning behind this tradition.
We have a good relationship with them but we are curious as to how they must view us. Why is it okay for them to ask us to "work" during their Sabbath? Do they then consider us inferior because we are doing these neighborly favors?
The Aish Rabbi Replies:
You are describing a phenomenon which is colloquially called a “Shabbos Goy.”
In essence, your neighbors should not be asking you to do things for them, which they themselves are not allowed to do on Shabbat. This is a Talmudic principle, as derived from the Torah which states that on Shabbat, "creative activity should not BE DONE for you" - i.e. even if you are only asking someone else to do it.
The only exceptions are: when there is a commandment to be fulfilled, great monetary loss, or a health-related situation. Air conditioning is considered health-related, because if things get too hot, people (especially the elderly, etc.) could faint or be exposed to other dangers.
Even in the above-mentioned cases, a Jew is only allowed to ask a non-Jew to do a rabbinic-level action. (Mishnah Berurah 307:19-24)
They certainly do not consider you inferior. Rather it is simple pragmatics: they are obligated in observing Shabbat laws that you are not. You can consider it a great kindness to be helping them out, just as any good neighbor would.
In recent times, Colin Powell, Mario Cuomo, Martin Scorsese, and an adolescent Elvis Presley assisted their Jewish neighbors in this way.
See also this article from Chabad.org.
But all those things aside, you would need to contact the rabbi of the particular community you are interested in servicing. You should tell him everything you have told us here. Then, if he is in need of your assistance, he can instruct you as to what work a non-Jew may do for a Jew on the Sabbath. Believe me, the laws can get complicated. Many religious Jews do not even know them.
Note that not everyone community is in need of a Shabbos Goy, and not everyone wants one either. You are correct when you say the idea is sort of out-dated.