This has never been much of an issue in my experience.

When you go to pay income taxes each year, they don't care about those things.

@Eli Frederick Be very careful purchasing homes that have been damaged and are located within a Special Flood Hazard Area.

Be careful and trust the person you’re partnering with.  

Sign a lease for Exactly one month at closing, have a hold back of an xtra $10k or so to protect yourself/motivate the seller.

If my property prices fall 20% I quite literally don't care.

Roth IRAs cannot be transferred to Solo 401k plans.A few other Solo 401k benefits: Compared to an IRA, Solo 401k contributions limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.

Would you care to give any advice on investing in the area (strategy, locating deals, financing, areas to avoid) 

Facebook Marketplace is even worse it seems...I swear many of them are just trolls trying to see if you’ll violate fair housing laws so just be careful in your wording in responses and be consistent.  

You could always report to your local permitting agency, not that that help your relationship with your neighbor, if you care.