A 70' tilt tower is very expensive. Might as well buy one of those telescoping towers, either a simple mast type or the more expensive crank-ups. US Tower sells a bunch, so do others.
US Tower
Used 70' self-supporting? You might luck out and get a decent one, but like Jim said above, many have structural problems. One just came down last week north of Bowling Green, about a 250-300 footer. It had been up for many years, and they knocked it down into the farmers field and cut it up. If it had been any good, space would have been rented on it.