So if I understand sub to, you're basically assuming the mortgage.

  $200/month divides into the $100K initial negative equals 500 months to recover the initial negative equity.Let's double the cash flow to $400/month.  250 months to recover the initial negative equity so over 20 years.Let's reduce the negative equity position to $50K (which likely is less realistic than expecting $400/month cash flow at that rent point), you are at over 10 years to recover the initial equity position.Now let's do it with all cash, no financing.The 50% rule state $900/month cash flow.  900 * 12/200K = $5.4% or about half of lifetime return of S&P 500, or what can almost be achieved with a zero work, zero risk CD.I see no way that someone who understands the numbers will call this a good investment.Note just because an investment is better than most other investments in a market does not imply something is a good investment. 

This is actually quite helpful insight in understanding the reasoning. 

There are a couple of unique tax laws to real estate investors - 1031 exchange, bonus depreciation on certain improvements, Qualified Opportunity Zones, real estate professional status, etc.Make sure that the accountant you interview to understand the above concepts.best of luck!

If both houses were sold in 2024 then the loss will negate the profit from my understanding.

A quote with no cost breakdown can definitely be a red flag—it makes it harder to understand what you’re paying for and leaves room for unexpected costs to pop up.

The more rehabs you do the better understanding you will have of the market for contacting work and materials.Doing a rehab every so often prevents you from being sharp with your budget.For those with limited exposure, ask others in the industry and always run your numbers based on being overbudget and overtime. 

As someone actively investing in STRs and looking to scale, this raises some concerns for me about the long-term viability of this strategy.I understand the tension between hotels and STRs, especially in popular tourist destinations, but I’m curious:How real is this threat?

I thoroughly understand what you mean.  

I understand I cannot legally require them to respond, unless the notice specifically requires it, like for instance, a notice of entry, but it's making it difficult to manage the property, and I'm not sure how to proceed.