Re: Please tell me this is a nutty idea so I will stop looking at this boat.
Look at as many boats as possible. If you find boats one boat on Craigslist that is interesting then find all of the other ones in the same marina (especially if it is far away) that are for sale and see if any meet your parameters. Set up appointments with sellers to look a multiple boats back to back. Once in a marina, especially if it has locked gates, walk the docks and look for other boats for sale. Talk to friendly owners and ask what they like and dislike about their boats, especially if their boats are in your target size range.
When we bought the Catalina 25 we were looking at 3 or 4 boats at a time. When I bought my Pearson 28-2 my parameters were tighter but I still made days where we could look at many boats on the same day. The day that we first looked at the 28-2 we also looked at an Islander 30, Freedom 28, and one or two others. All of those were about a 2 hour drive from our house, so I made as many appointments as possible.
The Don Casey book on inspecting the aging sailboat is a useful reference for what to look for when first looking at a boat. Once you find what you think is the right boat I do think it is worth paying for a survey. However on a simpler boat (like my Catalina 25) it is pretty easy to self survey if you can do so with an open mind. The best reasons for a mechanically inclined person to pay for a survey is that it often helps with negotiation and it gets you an impartial opinion.
It's rare for boats to be on the hard here (Seattle) since people keep them in the water all year. So I can't comment on that question.
Dirty isn't a big deal if the essentials are good. I'd place more importance on the condition and quality of consumable items like sails, rigging (standing and running), canvas, the engine, batteries. Replacing all of those items with new ones will cost $10k on a 25' boat.
A dirty boat with good condition equipment is easier to get going than a clean boat that needs new sails, has a 30 year old outboard, and needs all new standing rigging. However it's more common to find the clean both with good equipment or the dirty boat with old equipment.
It's worth spending more money to get a boat that has been recently loved. I bought my Catalina 25 for $4000 but sold it for about double that. However the buyer (who is a friend) got a better deal on that boat than I did since I had done about $8000 worth of work to it (new cushions, sails, running rigging, lighting, electrical -- it all adds up). He offered more, but I sold it to him for what I thought I could get for it on CL. When I bought my Pearson (at about 5x the cost) I made a high priority of looking for a boat with good sails, cushions, engine. I've still spent about $5000 on it replacing hardware, adding an autopilot, upgrading electronics, and doing bottom work. I knew that I'd spend this upfront and when considering boats I weighed what each of them would cost me in first year work. The Pearson that needed an autopilot and bottom paint was a much better deal than the Islander 30 that needed a new engine, bottom paint, and sails...even though the asking price on the Islander was $5000 cheaper.
I'm no longer participating on SailNet.