It is anticipated that developers will become more selective in where they choose to build, seeking out markets that are more affordable and have less government overreach.Whether it’s the lack of materials or labor, overall shortages complicate the construction industry.

Could get complicated.

That said, I do like the structure of having a defined business with an EIN and a bank account that is really run like a business and files tax info for all the properties in one place consistently from year to year, and it seems like a general partnership might be the way to combine these options.I don’t mind filing a 1065 and might even prefer it over putting all the details on our 1040, so I’m not trying to avoid that particular complication.

The STR market here is a bit complicated due to HOA regulations that almost never allow them, so I always recommend to make sure that the unit pencils out to at least break even as a standard rental in case the HOA makes a fuss. 

But now that it is my second purchase, and now that it may be more complicated with higher interest rates and potentially needing to get a loan for repairs too, I want to read up on how mortgages work (+refinances, ARM's, etc.). 

When you are working with the right kind of loan for an IRA, it will work, and most of the complications you note will go away.It will look like this:The LLC will purchase the propertyThe LLC will obtain a non-recourse loan for the purchaseThe LLC will receive the rents and pay the mortgage and other expenses associated with the propertyThe net cash flow will be tax-sheltered gains to the IRANote that when an IRA uses mortgage financing, the percentage of the income that the IRA receives as a result of that non-IRA money in the deal is taxable as Unrelated Debt-Financed Income (UDFI). 

Some have suggested house hacking SFH instead to avoid these complications but I can't seem to find information on how easily single rooms in SFH in Vegas rent out, at what prices, etc.

It complicates my financing situation a bit (I have a written agreement to up the funded amount to 80% of an agreed to ARV if repairs are completed within a year).

It all gets extremely complicated, and doesn’t necessarily seem logical, but it’s the tax code.  

In most cases, neither is warranted.Warning: I am not an attorney and this can be a complicated topic.