If you still want to rent out your other bedroom you can have a tenant in the opposite side AND a roommate which would give you two income streams.

However, with a SFH you will lower your standards when vacancy arises more than one month as you have no income coming in to male that payment.  

I was interested in something like owning a rental property as a way to generate some additional income. 

This is much lower than the costs associated with refinancing.Benefits of Mortgage RecastingLower Monthly Payments: The most immediate benefit is a reduced monthly payment, which can free up cash for other financial goals.Save on Interest: By reducing your principal balance, you’ll pay less interest over the life of the loan, potentially saving thousands of dollars.No Credit Check or Appraisal: Unlike refinancing, recasting doesn’t require a credit check, income verification, or home appraisal, making it a quicker and simpler process.Keep Your Current Interest Rate: If you have a favorable interest rate on your current loan, recasting allows you to maintain it while still lowering your payments.Drawbacks of Mortgage RecastingRequires a Lump Sum: Not everyone has the cash on hand to make a significant lump sum payment, which can make recasting inaccessible for some homeowners.Doesn’t Shorten Loan Term: While your monthly payments are lower, recasting doesn’t reduce the length of your loan.

Income approach Also known as the rental income approach, this method estimates the market value by analyzing the property's anticipated future income and converting it to a present value estimate.

The owner should look at it more like a DSCR, and should be pricing the property and offering terms such that the income from the property is adequate to pay back the loan.

Kudos to you for doing something to create a secondary income stream. there are 5 income streams in RE rentals, possibly six if you do things a certain way.The reality here is your model (buy box) is suffering from too high an entry and too high a cost of capital.

I do a lot of private lending and we do make some passive interest, but the good fixing flippers make the bulk of the money.

For all methods you would want to find a market that has strong employment rates, strong income rates for the market, and is a growing or an established market. 

In Italy your second house or even a duplex section the income is taxed higher.