I am a 58 year old retired teacher looking to invest in rentals to supplement my income and pay off current mortgage. 

@David Antunes 4 unit properties are residential...valuation is comparable sales method...in very rare instances you'll see income approach...but only as supplement.

I have some good automations built out for mine as well that automatically emails my housekeeper when I get a new booking and sends emails to my guests automatically during their stay that I supplement with Evolve. 

It's very stressful trying to decide what's the best way to invest the small amount of money that I have, especially knowing that the decisions I make will affect how my retirement is supplemented in about 10-12 years. 

If existing sheetrock can be replaced (or supplemented with) a product like Quiet Rock (sound dampened sheet rock) or Green Glue (sound dampening material that goes between sheet rock / drywall layers) I think you would get a significant reduction in conversations being heard in adjacent rooms.

It might take you some experimentation to find the right type of housing combined with the right tenant pool so that cash flow could supplement or replace income.

You then develop a "master plan submittal" set, which typically includes all floor plans + options, exterior elevations + options, and all supplemental plans (details, electrical, etc.).You then develop "site-specific" plan submittals that represent each specific site condition.

Its much like being on Supplemental Security Income or Social Security Disability, you don't trade them back dollar for dollar (though the trade is a less generous 2/1 pre-tax).

Banking cash to live on (extra 500k) to use an extra $50k a year as an income supplement.

My wife and I have owned a SFH in the Natomas area since 2016 but have supplemented the mortgage payment by renting out the spare bedrooms.