@Jacob Ritter, Taylor really hit most of your questions. Your questions do amount a bit to: how do you start a business? Well, there are thousands of ways.
But to help answer as best as I can:
1) LLCs are most common. A lot of people just buy a house personally too and rent a room to a friend or rent it out (just make sure you are not violating terms of your mortgage if you buy as owner-occupant and don't occupy it)
2) Generally, your biggest tax advantage is the depreciation you get, which often times will more than offset your profit. BUT, the IRS always gets their piece, so you will owe more tax on the sale when you have depreciated your property.
3) I would not say there is ever an auto-pilot, but just starting out, the best bet is to find a great manager. This can be a property manager, if you plan on investing directly. A syndication group, if you plan on being more passive. Or a great handyman, if you plan on managing your own. I began investing on my own, and managed all my own properties while working full time. 6 single family homes was pretty easy, provided great additional income, and I had more than enough time to focus on my career.
4) Excel is the standard for creating models. As for property management software, it depends on what you are buying. One single family rental, you really don't need anything. Track revenue and expenses in excel and send to your accountant. I started using Cozy.co to give my tenants the ability to pay rent online with either credit card or ACH. I have seen large 100+ units under management use Appfolio, and then you get into Yardi and its competitors for the very large scale owners/managers.
I cannot recommend quickbooks enough though. Most accounting firms use it, and while it is not the cheapest, it is powerful and saves me a lot when it comes to tax time.
5) This really depends on what you plan on starting with. A house-hack duplex or 4 family, a single family rental, joining a syndication group. For me, I own single family rentals and duplexes. I am very glad I purchased a house and lived there for 3-4 years before I bought my first investment property. I learned how much a furnace cost, how much a water heater cost. I had to fix leaky faucets, etc. Additionally, build your network. I used the same handyman, who I got from a coworker for about 8 years, until he finally started doing bad work. But in those 8 years, I was able to meet and build out a roster of others so I didn't have skip a beat.
6) Again, this depends on what you are buying. Typically, you are either looking for a residential lender or commercial, depending on what you buy. Residential will handle 4 units and under. As soon as you get to 5 unit buildings, you are in commercial. You are also in commercial if the property is not owner-occupant or owned under an LLC. There are entire forums here focused on lending, so you will have no shortage of resources to access once you determine what you are buying.