Hi @Carl Hammill - welcome to BP!
- Easements: In my opinion - these are important when you encounter a landlocked property (which isn't necessarily a common thing, but it does come up from time to time) and/or if your intent is to somehow develop or subdivide the property yourself (which isn't something I typically do, and 95% of the land flippers I know don't get into this in a big way). It's great to understand how these work and how to identify them, but I wouldn't say it's a necessity in order to get started. I wouldn't feel like you need to be an expert at these before you start making progress.
- LLC: If your intent is to be in the land business long-term, it's a great practice to have one of these in place... but again, I wouldn't say it's an absolute necessity (and frankly, it can add a lot of complications and confusion, especially when you're just getting started and trying to figure out what you're doing). I've seen a lot of people start out buying and selling properties in their personal name, and after they've done a few deals and proven the business model to themselves, THEN they form an LLC (note: this is not legal advice - just an example of what I've seen some people do). In terms of forming one in each state - honestly, I think it's best to get really familiar and find success in one state and then branch out and deal with the added complications of working in multiple states (a lot of laws can change from state-to-state, so again, it'll just add to the confusion if you choose to work all over the country from the very beginning). It's certainly doable, but also a bit harder.
- Seller Financing: It's an awesome way to create monthly cash flow and add financial stability to your operation, but once you decide to get into this realm, you'll have to learn quite a bit about documentation, how the laws work in your state when (not if) people stop paying, how to manage loans and collect payments (among other things). I think it's definitely worth learning about and pursuing if you want more of a "passive" (if you can call it that) income from the business, but it's also one of those things that has some wrinkles to iron out once you get into it.
- Closing In-House: It's definitely possible to close in-house (and when the deals are cheap enough, it may be the only economical way to do it), but it also takes quite a bit of time and work to learn how to do it correctly, to make sure the paperwork is prepared correctly, and then to actually execute it. Again, I think it's definitely worth learning and understanding how it works, but you should also be prepared to go slowly and make sure you're doing everything correctly (and if you're not willing to do this, make sure the deals you pursue have enough value to justify paying a title company to close on your behalf).
- Mail Copy: You don't need a full-blown course to figure out what to say in your mail pieces. I've got several examples I can show you (PM me and I'll send you a few links). There are a thousand different ways to write your mail pieces, and many of them can work just fine.