1. How often should I change the bedding?
It depends on your set up, your bedding, if you will be using poop boards under the roost boards and how much they are in the coop VS the run. It could be monthly, every 6 months. Hard to say.
2. What is the cheapest chicken coop model and brand?
You don't want the cheapest, you want a secure coop. You can re-purpose material and make your own very cheap, if you want to or can. Don't buy a prefab coop, they're the worst and won't hold up more that a couple years or so.
3. How often should I let the chickens out?
Daily in their secure run or free range depending on the predators in your area. This can include your own pets, along with wild animals.
4. Will chicks survive out in the open?
They really need a secure coop to sleep in, for their protection. Can they survive in the open? During the day I would say, it's possible if you don't have any predators. I know people that leave theirs out all day but your taking a chance of something happening to them.