So you wind up paying double the principle if you bring to maturity, but you can break the contract after 6 months. 

This allows you create per property P&L statements, and also an overall P&L that "rolls up" all your properties together.While Quickbooks is more complicated than some other options, if somewhat forces you to understand basic accounting principles. 

It's much more important in the long-run to learn the basic investing principles and decide what type of RE investments you want to specialize in. 

If your principle, interest, taxes, and insurance are $2,500 a month, that only leaves $500 for maintenance, capital expenditures (roof, furnace, flooring, windows, etc.), vacancy, etc.

House: ~1300 sq feet, 3BD/2BA, completely re-done.Loan Amount: $131,250Mortgage (Principle, Interest, Taxes, Insurance): $1,115Vacancy, Repair, Etc: $100Total Expenses: $1,215Proposed Rent: $1,600Cash Flow: $385Cap Rate: ~%10

What I do know is that I've made 4% on my money over the 10yrs, I'm only getting taxed on the interest earned, not the principle that is getting paid back to me monthly.

I am looking to borrow 50K at a 6%-8% interest rate and am planning to not take out any money with projections to pay back interest and principle in full within four years.

Would I be going against the principle of making the deal in the buy if I buy at 50k?

Over 8 months I payed down a large amount of extra principle.

If you were in MN I would recommend you take the MMHA principles of property management course, they cover this quite a bit.I have accepted Section 8 in the past and it was always a hassle.