Boat Kid,
Don't let the high numbers discourage you. If you are careful, you can find a boat in your range with annual costs that aren't too high (Certain high cost areas will increase the costs significantly). On a limited budget (it's ok, everyone starts somewhere), don't be tempted to go for the bigger boat, but instead get one that you can sail right away without having to rebuild it, even if it's smaller.
When you have a fixed amount of money, the bigger the boat at preset price, the more likely it is to have problems that will require spending lots of money to bring it up to sailable status. No question about it, the bigger boat is generally has more room, more aminities, and can make cruising more comfortable. But bigger requires more expense in everyway, and buying a cheap boat needing lot's of work isn't likely to save money in the long run, because it's cheap because it doesn't stack up as well against one the same size that's been maintained well....it's pay me now or pay me later (with repairs and lots of time/money...and hours of work...trying to bring it up to the standards of that somewhat more expensive boat of the same size that you can use to go sailing now.
If you buy a trailerable boat (21-24 ft. for example):
You have a lower initial cost ($5000)
If you buy one that is ready to sail now without rebuilding, you don't have to spend much in the way of maintenance/upgrades.
Keep it simple, you don't need all the fancy gadgets...a simple hand held GPS vs. on with chartplotter. Get the basic things, avoid fancy, even if they are nicer.
You will save on slip fees because you can keep it at home.
You won't have to haul it out every year or two to clean/paint the bottom.
Systems are simple and you can do most of the repairs yourself. You can, to a great degree, control the amount of repairs if you take care of the boat...sailing to the extreeme in extreeme conditions tends to break things, and boat repairs/parts are horribly expensive (~3X that of similar repair on a car).
Your insurance costs will be lower (maybe $250/yr.)
Your property taxes will be lower (maybe $200/yr.)
Your maintence costs shouldn't be more than $250-500 if you don't have major replacements.
This boat is not going to be as shiney as a new one, but it'll sail just as well.
Now if you want restored and shiney as new, you are going to start pumping lots of money and work into it. Pretty comes at a price in any size.
Now go to 25-27 ft.
It's a lot more boat, more room, sails more solid, etc., but more expensive.
Initial purchase price $5,000
Repairs/upgrades to bring it up to go sailing conditions (still not shiney) (maybe $3000 to $5000)
Slip fees since you have to keep it in the water: (maybe $2,000 to $4000) depending where you are.
Haulout and repainting the bottom every two years (maybe $1,000 if yard does it)
Insurance (maybe $300-400/yr)
Property Taxes (maybe $300-$400/yr.)
Routine upkeep beyond restoring (maybe $500 - 750)
And you still have a boat with lots of dings, but it sails just like the fancy new one.
The trailer boat is a bit of a pain raising and lowering the mast and launching each time you use it, but this is what you give up to save on costs. A boat in the slip and a little bigger is nice and adds to the pleasure, but it comes at a cost.
Hope this helps. Go for it. I think you and your parents will enjoy it. Both size boats sail and get you out on the water.