Hrm..... I have been sailing since I was 8. Owned boats since I was 12 (if my sunfish counted). At 25 I was sailing a Hunter 22 around the Chesapeake Bay in a similar situation to you, except I did have a bit of experience and I would take longer cruises.
At 32 I am now in a Catalina 30. I wouldn't want to go back to trailer sailing as the set up and take down time costs you a bit of sailing time. Once every two years I pull the boat out and do the big maintenance to it (sanding, painting, and other fun stuff). I can get to my boat (it is 5 minutes from my house) and be out of the slip in less than 10 minutes.
Trailer sailing, what I did for a few years, was okay but you always had to have help and the boat was small for long trips. I ended up putting my boat into a slip for my last year of owning the Hunter 22 because I was wanting to single hand more (my ex didn't like the boat much) and I was tired of raising and lowering the mast.
If you don't want to slip the boat and you don't want to raise and lower the mast constantly, find a marina that will let you store your boat on the trailer and be able to keep the mast up. This is probably the best way to trailer sail and it is cheaper than being in a slip.
Will they take you serious if you are 25 and walking into a marina? YES! It is good to get new blood into the sport and most sailors will gladly welcome you into the rowdy crowd! I was never scoffed at because of my age. You will find that sailors are a very diverse bunch but they all come together over one thing....sailing. If you don't mind being the youngest person in the crowd then you will get to meet some interesting people.
If you end up having bigger water and liking the cruising, then you will start looking towards bigger boats in the future. Don't let the boat scare you. They are not nearly as complex as they look and most of the maintenance is pretty straight forward. When I moved from the Hunter 22 to the Catalina 30 I was a bit nervous with all the systems that I have (pressurized water, diesel, more in depth 12V system, and a marine head). All of these systems, including the diesel, aren't that complex when you begin to look at them.
Don't forget that the cost of owning the boat can be kind of high. You have the boat purchase and those kind of things in the first part, but there is always something to do on them. You will have yearly maintenance like Woodwork, Sail repair, and other things along with bigger repairs that you will run into. It is similar to owning a car, but things tend to be more expensive. Budget for these items early on and it will help.
When I began to put my boat into a slip I began budging my tax return to cover this. My tax return covers my yearly slip fees, my haul out, my painting, and one other thing for the season.
Check you
www.yachtworld.com for a source on finding good boats. Craigs list is always there. Other sites are
www.usedboats.com and
www.boattrader.com
Good luck and enjoy. Learn all that you can about the boat and the waters that you are going to sail. Don't be afraid to stop and ask questions as most sailors are extremely helpful and will gladly give you some knowledge and share a story or two.