The question is mostly a personal financial planning question and it depends on your preference and what balance of risk and access you'd like and would be comfortable with.

Even with guaranteed rent, it's important to thoroughly vet applicants.

It will likely depend on where you are looking. 

For mobile homes, it often depends on whether the property is considered real estate (attached to land) or personal property (if it’s not).

However, after he saw the quantity of ADU applications come across his desk to plan check he went out and started his own consulting company.

Also look back on their application and see if you missed any 'red flags" so this can be a valuable learning experience for you.

This also depends on how are you calculate cash flow and what you're using to discount for expenses.

As for Nolo, is it applicable in all states?

With $50K and a DSCR loan, your budget will likely cap at properties in the $150K-$170K range, depending on the closing costs and any repairs needed.

In my experience, 75% of the time, the tax payer doesn't have a large enough liability to justify the accelerated depreciation anyhow- depending on your income and tax bill, it might not matter at all.