Being new to this, what are some known strategies that people use to purchase a second, third, fourth property quickly [within a couple of years] opposed to waiting for that single property to bring in enough income to afford the next purchase?

The Cash Flow is ridiculous.Over time, you get to understand that Cash Flow is something that only stays the same if you invested in something that is designed to do so like a Coupon Bond.Because I calculate the FUTURE Cash Flows out 10 years, I fully understand the true return of the Investments and how much cash flow I will achieve.The other thing to take into consideration is the Mortgage Balance reduction.If your investment is at break even but your Mortgage is a fixed rate, then one day, when that Mortgage goes away, your Cash Flow increases tremendously.When you take into account a 30 year projection of your Investment Cash Flows, you realize just how wealthy you can get by buying for FUTURE Cash Flow as opposed to Cash Flow NOW.It's really not RIGHT to pretend that the Cash flow you receive at the purchase is going to be the same throughout the holding period of the investment.

In fact, I did read them, contacted my attorney about a situation that came up and was being given opposing advice from two professionals.

I would never be opposed to using any of the processes you mentioned above, including the short-term financing, rehab, and then refinance into a conventional loan, but I would want to wait until after my first go around. 

You should be using it to generate income and earn it's keep as opposed to hoarding it.

But I am not opposed to turn key either, for the right price of course.  

@Brieyon McBride why not have a lawyer just prepare one as opposed to review one?

The only possible gripe you can have that would have some legs would be that they are sending you an owner statement as opposed to providing you with an online portal to possibly view things sooner but to expect them to call you about every minute detail the moment it happens is not a realistic expectation.

While I live in SD keep in mind I don’t invest here (not opposed to doing so.

It is far better to pay for something that will actually produce a immediate income as opposed to being a money pit.