I use craigslist quite a lot. For both selling and buying. If I respond to an ad and don't get an answer, 9 out of 10 times the item has been sold.
Using a sauna as a humidor does'it make any sense to me. What are you going to do, turn the heat down and throw water on cold rocks? Trying to keep the humidity between 65 and 70 will be a nightmare.
Buy a 1,000 count humidor. That will solve your problem for a few months.