@Hamidou Keita I would recommend if duplexes are limited if you can get a 4-5 bedroom house and either rent by room for house hack or splitting a big house into 2 and adding a kitchenette and separate entrance as a more cost effective ROI option 

However, nearing retirement, with our past experience in mind, we decided to try it again, this time just rehabbing one house to flip.So, I set up a self-directed IRA so we could use the retirement money we had left after the recession, and bought a foreclosure house that needed a lot work.

It's crucial to consult with a tax professional who understands the nuances of your situation to determine the most appropriate and cost-effective method for your tax filings.

2.What are the best and most cost-effective solutions for managing this potential long-term issue?

In Portland for example we are not allowed to increase rent more than once in 12 months, and it must be less than 10% increase in "effective rent".

Maybe self-accountability does matter. 

It's up to you how far to take this though.When we're faced with this, we try to hold the tenants accountable, by pushing hard to do self-showings.- Who better to show the house and speak positively about than a current tenant?

We own over 100 units in San Diego and have always self-managed. 

Quote from @Dallas Hoover: Want to acquire a self-car wash within Dallas Texas area. 

Apartments, Student Housing, Self Storage, Commercial, etc.The SEC classifies a DST as a security so they must be purchased from a financial advisor.The costs very A LOT by financial advisor and DST Sponsor.