But we also had a case where we had title insurance from a company and later there was a potential claim, and the company had gone out of business so the title insurance was no longer valid. 

Use a Warranty Deed, not a QCD.

Minnesota has also build a new public train which just opened a month ago to the public, I'm guessing this will bring value to the areas it operates, is my thought process valid?

If you encounter resistance, a nuanced interpretation of the statute can push that time out to 3 years.There are services that will verify the validity of the tax sale for particular providers of title policies in lieu of actually filing suit to quiet title.  

Your concerns are valid.  

If the appliances are in high-end units and are new, they may be under warranty for a year or two; if not, typical lifespan could be 5 - 10 years depending on the way tenants treat them.

Using a technique only valid in 17 states, I was able to buy the property with no liens attached.4. 

No, the Deed is a General Warranty deed under another person trust.

Considering the 4-month old system was still under warranty, I had the tech come out and look at it, simply to discover that the tenants did not change the air filter and that was causing the system to not run as cool as it should.

They heard half of something from someone without validating on their own.You could be 100% correct but would benefit others from CA on here if you can post the code.