If your only job and source of income is "landlord," the DTI math works out to about 2.5x.

The classes you will take do not teach you much about being an investor other than some basic math and a few key terms.

Depending on what your plans are after the 5 years fixed are up, this is a simple numbers (math) problem...as it always is.1 - Since you are getting $9400 back at closing, that means you are out of pocket 9400 less with the higher interest than the lower...which puts you 9400 ahead at the start.2 - Over the next 5 years, your cash flow will be about 130 less with the higher interest rate, however...3 - That only totals up to about 7800, which means over that 5 year period the higher interest rate waves you about 1700, but...4 - Since it will take you 5 years to reduce your cash position from a +9400 to a +1700, and if you invest the 9400 ASAP, the compounding effect on that immediate 9400 extra cash will make the minimal look of "only a 1700 savings" immaterial. 

Usually the answer is "No", because it's a math equation.

I was also considering using them but the math didn’t seem to make sense for me.

Your expenses are too low:Need management (10%)CapEx & Repairs should be closer to 7.5% eachMy math shows that your cash flow will be -$50/month, that's negative.

Do the math before hand and figure out how much it will cost you to buy land and build then do a market analysis to see what price you can sell it for. 

Bad news is, if you think you'll be into it for $100k over appraisal once all is said and done, this is a very simple math problem: if you were to sell it as is right now, would you lose more or less than $100k? 

I will try to do some math on the basic big items for now.

Am I doing that math wrong?