Using real world comps & calendars from your personal experience, local PM's, online estimators.

They get about $681 a bed and we estimate they can fit 40 beds.

The next steps will involve accurate construction cost estimates by a licensed contractor (or two) and connecting with a lender (possibly current local bank) for construction financing.

However, with mortgage rates being so high when I bought, I am worried I will have some negative cash flow (approximately 200-300 per month as a long term).

If not - what equation would you use to best estimate what a Net Worth Return a House Hack can have? 

What I really should've said is, "properties that approximately break even, making it more practical to hold in the long run."

Anyone with active listings in the area care to weight in on approximate summer rental income?

From looking at the website’s advertised interest rate (which was 2.75%) my impression was they were just looking at the date the property was purchased and estimating a mortgage payment based on the market rate at that time, 2.87% per Fannie Mae. 

I just got one last month that had been on the market for awhile and after moving out it's around 13% when estimating 10% Vacancy and 10% management fee, both of which I won't be paying on for a bit. 

J Scott also has a book on estimating rehab costs.