I don't see why you'd think the Olson 25 is going to cost more than a Cal 25 in maintenance. They're both pretty simple boats.
Is the $3000-6000 figure your budget for buying the boat??? If so, you're probably going to be unhappy with most of the boats in the price range...most will be pretty beat up or in need of refurbishing.
Any boat you get is going to require a fair bit of maintenance. That's just a fact of life—boats require maintenance—either you do it, or you pay a lot more to fix stuff later.
Most boats <30' LOA can be singlehanded, especially if you modify the running rigging to make it easier to do so.
I like the Ranger 26, which a friend of mine owns. Another owns a Columbia 26...both are pretty nice boats... with fairly active owners associations IIRC.
Some of your objectives are somewhat mutually exclusive. Fast boats that win races generally have higher maintenance costs... Racing boats, especially smaller ones like the ones you're talking about, are often less seaworthy than slower designs.
For instance, the J/24 is a great little boat and has a huge following and is raced almost everywhere... but the boat has serious issues when sailing in heavier weather. Many have been sunk because someone forgot to dog the cockpit lazarette locker and the boat flooded after a knockdown. One sailing school I know loses a J/24 about every other year due to this...
That Olson 25 looks like exactly the type of boat I'm looking for, but it seems maintenance costs would be higher. Also, they seem harder to find. If I'm wrong in these assumptions, please speak up.
Here are my priorities: (Basically - 1 Money, 2 Performance, 3 Cruising)
22-25 feet if not trailerable (slips are cheaper/more available at under 25')
22-30 feet if trailerable (who needs a slip if I can use a trailer?)
Low maintenance (doesn't break, cheap parts)
Handles high winds
Fastest time around a circuit (can cut steep tacks, especially)
Plenty of race opportunities
Makes headway in very light wind
Large community of boat owners
2 people can sleep for 3 or 4 day cruises
Can sail solo (I'd like to be able to sail the main and jib solo)
As a bonus, can handle inter-island voyages in Hawaii (less priority)
I've also looked at the:
Albin Vega 27 (too slow, slightly too big, I like the deep-ocean capability)
Olson 25 (low availability, smaller community)
Catalina 25 (can't handle stronger winds so well)
C&C 24 (can't hold to windward as well, but it's trailerable)
Ranger (I sailed one in 2 knots of wind once, but can't find any info on it)
The Cal 25 seems to be calling me the more I read about it. Cheap, good Cal community, very available, Cal races almost anywhere I would live.
How does the Cal 25 compare to the others I've mentioned?