Maybe they are grinding up garlic or onions or who knows what.

With that in mind, I’m considering purchasing four rental units over the next four years to build a stream of income that could help supplement my retirement by age 68.The challenge I’m facing is that the deals I’ve come across so far don’t make financial sense.

It's an estimated cash on cash return given current rental rates subtract expenses assuming 7% interest rate, 10% management fee, 5% repairs, 5% capex and other expenses like mortgage, insurance, tax. it's a estimate to tell you what properties to analyze vs ignoreyou can see the are pockets of negative returns as well as pockets of positive return. this is to supplement the data @Devin Conley provided

- The market is in a little bit of a lull right now (buyers market), its a great time to buy, but slower time to sell (my primary business is flipping houses) I can supplement my flipping business by providing project management services/consulting, helping investors find discounted properties, etc. etc.

I'd be heavily focused on mitigating that future tax liabilty rather than directly supplementing that income.

I also helped my mother get 2 rentals to help supplement her retirement, mistake #1b.

Unless there is a history of STRs in the property already and you have experience with STR, you really wouldn't be able to supplement your income with that. 

It's not quite as easy as renting out two sides of a duplex, but with the right marketing and management you could rent out the extra unit to supplement the mortgage payment. 

Ask the builder or their legal representative for a copy of the CC&Rs (Covenants, Conditions, and Restrictions) or any supplemental documents specific to the development.Financing Considerations: If you’re financing the property, some loan types have limitations on renting out a home within the first year.

I have supplemental insurance so I am of the mindset that they should get rid of this bogus insurance and lower my host fees..