This is because collecting rent is often seen as passive income, and the state may not consider this "doing business" that would trigger the registration requirement.However, states like California or New York may have specific rules, so it's wise to check state-specific requirements.Active Income (e.g., House Flipping):Active Business Operations: If you are engaging in activities like house flipping, property development, or property management, this would likely be considered active business operations.

As far as sprinklers in rehabs, is there a hard and fast rule used?

I do see the 1% rule in 80,000-150,000 range in Memphis

A 1031 exchange requires a fiduciary to receive the money and has strict rules around the whole process.

Mind Excess Business Loss Rules.

Then there's the issue with doing a 1031 which is fine but my property taxes would go from $2200/yr to $4400/yr for an identical home. 

Art Cost Basis Rules Clarified by IRSBy: Spencer M.

Quote from @Anthony King: Are there any rules/regulations regarding private lending from family members?

This is the new FinCEN rule where you do have to report beneficial owners or those who have substantial control to the government watchdogs.

You can find 1.5-2% rules all day.