As to the self sustainably of the village, I disagree with the statement that 25 people don't have the needs of a general store. A general store is probably overkill, but a local trade stand is right up their alley.
So without being overly analytical, think about this...
A stable is used to house horses for visiting people, how many visitors will a town of 25 have? A stable is overkill.
A tavern or inn - again inns are for housing visitors, see above. As for a tavern, if you do have one, think of all the uses it will have outside of just a bar. Having grown up in a small town our "tavern" was the local firehouse. It housed the town council meetings, community dinners, the local teen rec center (such as it was). So it may or may not be open, when the adventurers pass through (maybe they are meeting about the problem at hand).
A farming town will have food, possibly wood (depending upon the local flora), maybe flax for clothing, a mill (great catch Gilladian) now whether its driven by water or horse is up to you, and a smithy to make tools is probably not unbelievable.
But where are they going to get their shoes? Wooden items? Crockery? Tack and harness for the animals? How about the alcohol for the tavern? If it's a totally fantastic world, maybe there is a mage employed to create items or something, but don't forget the small stuff. Who knows, maybe the kindly local trader is the culprit. *waggle eyebrows/evil grin *
There are tons of books and resources about small medieval/fantasy towns - you should check them out.
