I am looking for a "road" bike for my wife. She currently rides an old HT of mine with slicks on it and as she rides it more, it makes sense to get her a bike that fits her. As our road rides typically involve some dirt roads, I think a mountain bike with slicks makes sense. She likes the upright stance on the mtb, I don't think she'd be comfortable on drop bars.

We're looking for something relatively light, old is ok, but cheap is a necessity. Front suspension would be nice, but not necessary. If anyone has a frame/fork that fits the bill, I could look at that as well. The bike she's riding now is a Cannondale, so I could even use a frame only with a fatty head tube.

My wife is 5'7" with a 32" inseam, so a 17-18/medium frame would probably be good.

A formerly nice older mountain bike would be great.