The $ factor is almost irrelevant lately, if you are able to be patient and watch for deals. Lots of 4x5s that are pick up only on ebay go for very short money.
Similar deals exist on Craigslist. Then there is networking, I was recently offered a 4x5 with a color head for free.
The patience part is waiting for one to show up that's within resonable driving distance.
As for lenses, you might be able to get away with a 50 for 35 and 645, though an 80 would be better for the 645 negs. If I were going to start with just one, I'd use an 80, however.