Jared,
It seems no one really answered the question of costs to start up a biz. Here's the quick and dirty:
LLC formation: Around $250 or so depending on your state filing fees. If you only have a single member LLC then you can safely use online services like LegalZoom. If you have multiple members or anything else weird then use a local attorney and you'd be looking at $1000 or more.
EIN: $150. As a business you need to have a federal EIN. You can easily file for this online yourself.
Insurance: Don't need until you have a property, and then biz coverage can be included as part of this. Amount depends on where you are and what the property particulars are.
Website/domain: You don't have to have this to get started, but if you choose to they are also relatively inexpensive. Domains are as little as $12/yr.
As for your business plan, Steve L. summed it up pretty well. I've been involved in starting several businesses and have gone through the oh-so pleasant activity of raising venture capital. Realize that no one is going to read your business plan. Writing a biz plan is a good activity for you to fully think through what your plans are, but that's about where it ends. Don't expect it to be useful beyond that.
Good luck!