There IS a directory for Ren faires in the country, but they usually only list the big established ones.
Many faires that are a decade old or older, will have already established rules for readers. For some it's a matter of coming up with the money to rent the space... and if they have the same fees as for a craft vendor, it wont be cheap. Somew even make you buy a booth...and then you have to rent it for the season as well!
The other thing about established faires, is that they usually only have room for so many readers, and if they already have their number, then you are on a waiting list for future openings.
Itr's good to go to your local faire, and talk to readers there. Some will be rude, because they don't like the competition...but most will be open and helpful. Sometimes they look for an extra reader to fill in thier booth, or be there as back-up.
Still...there are many many faires that crop up each year that are new, or are open for one or two weekends, and it's easier to get in on the ground floor, for a reasonable cost.
I agree...google Renaissance Faires...in your local area...and you will probably find a few small ones that are open in the Spring!
And the best advice I can give on this...is learn an extra divination skill that no one else around you is doing...do tarot PLUS oracles...or angel readings, or learn astrology, palmistry or tea reading. Lithomancy or sortilege is also an awesome draw.