You will need to apply for permits or some angry neighbor will call it in and complain. They would then force you to take it down. Don't assume you can get away without one!
If you're going to be spending that kind of cash you will want to at least have a plan laid out, it will save you a lot of money in the long run. Some basics heights, etc will help you to know how much lumber you need. And let me tell you, buying those bolts individually isn't fun! They cost about 300x's more that way, and that is NOT a joke!