There is a gentleman over here that gets the used railroad ties dropped off from a maintenance crew. So it's fairly cheap, you just gotta take the good, the bad, and he will let you pass on the ugly. He still has over 5,000 ties if anyone needs any in southern Indiana. You do have to load them yourself.
I put the first row on concrete footer then the rest are anchored with 1/2" by 2' rebar. There is roughly 3 to 4 per tie. I also put dead mans in every third row up and no more than 16 feet apart. I think it was 8 dead man's in the final project and 226 rebar pieces. Couldn't have done it without the tractor.