To figure the expense of furnishing, you could use this rule of thumb: $10-15k for the unit itself (things like appliances, living room furniture) and $2-3k/bedroom.

Now that home prices have stabilized, every month you hold a NPL it becomes less valuable because homes are not appreciating and time costs money, as well as additional incurred expenses like servicing, FPI, legal etc.

The home is in good shape and would not necessarily be a good BRRRR because rental comps wouldn't cover the refinanced PITI (plus expenses). 

If using a PM, they are expensive and often bring the return in line with LTR.  2)  STRs and MTRs are at risk of increased regulation.  

@Nate P.Your profile hints that you are living abroad.If you are a US citizen - you want to make sure that the CPA you work with understands the foreign earned income exclusion(FEIE).If you purchase a property and are expecting valuable feedback on how that property will impact your tax return, you will need to provide a rough profit and loss projection(rental income and expenses) along with purchase price to have a conversation with your accountant so that they can provide you good feedback. 

Step 1 is getting your expenses to bare bones, next to nothing cost of living beyond the basics.

i know that's a big expense... but so is buying the wrong property and getting hit with thousands or tens of thousands of dollars in capex

Working with design-builders can be incredibly expensive.

They might want to hold the property in an LLC, and have its own bank account for expenses

Net Operating Income is simply your income left over after all business expenses, not including principal, interest, or any reserves (since those aren't expenses yet).