I would assume that these balances quickly and frequently exceed the $250k?

I know the Kwak Brothers speak about this frequently as well, I've found a few websites that promote it or speak about it as well.

If you don't replace items frequently, the quality of your product decreases quickly.As for insurance, I truly haven't experienced this phenomenon. 

Happy to connect with you as I frequently work within the NC market.

Happy to connect on this as I'm still actively brokering deals (commercial) in Washington all the time and I'm frequently traveling up there to view properties and meet with other brokers.

Are multifamily frequently put on the market? 

If we did, it means we need to have that hard conversation and get a new cleaning team.When we find a cleaning deficiency, we will send our inspector out more frequently in the subsequent turnovers.

Here are the Fannie Mae guidelines for legally non-conforming properties:If the Property's characteristics are legally non-conforming, you must:ensure the Borrower executes the Modifications to Multifamily Loan and Security Agreement (Legal Non-Conforming Status) (Form 6275);confirm whether, if fully or partially destroyed, the Property's Improvements can be fully rebuilt to the pre-casualty condition per current laws, zoning requirements, and building codes; and if the Property’s Improvements cannot be fully rebuilt to the pre-casualty condition, evaluate if the as-rebuilt Property will support the Mortgage Loan at the current Tier, and document your analysis in the Transaction Approval Memo.To assess the Borrower's ability to rebuild Improvements on a non-conforming Property to a level that will support the Mortgage Loan at the current Tier, you should consider: conducting a threshold analysis to determine the resulting actual amortizing DSCR if the reconstructed Improvements cannot be rebuilt as-is per current law; the likelihood of a casualty event (e.g., wind, earthquake, fire, flood, mine subsidence, etc.); the percentage of damage to the Improvements at which the Property’s jurisdiction will require the Property be rebuilt to current zoning and land use requirements (i.e., the destruction threshold); which Property characteristics the destruction threshold percentage applies to, such as market value, assessed value, replacement cost, or unit count; for Properties with multiple buildings, if the destruction threshold percentage applies to each building, or all buildings as a whole; the replacement cost to rebuild per current requirements for zoning, and land use; the Property’s continued marketability, and economic viability; the amount and type of Borrower-maintained insurance coverage required per Part II, Chapter 5: Property and Liability Insurance, Section 501.02C: Ordinance or Law Insurance; insurance loss proceeds payout, compared to increased rebuilding costs, including from building code changes, Americans with Disabilities Act compliance, and the municipality's local zoning requirements (e.g., green compliance for new buildings, etc.); the sufficiency of estimated insurance proceeds from ordinance or law insurance and other coverages to repay the Mortgage Loan in the event of partial or full casualty, or condemnation; and for a Tier 3 or Tier 4 Mortgage Loan, if requiring execution of the Limited Payment Guaranty (Form 6020.LPG) would mitigate the risk of the as-rebuilt Property not supporting a Tier 2 Mortgage Loan.

STRs depend on seasonal demand and can have more frequent vacancies, while LTRs provide steady, predictable cash flow with longer leases.

I will say this is a strategy that is promoted on these forums frequently.