Only thing you can do is factor It into your numbers.

However, this depends on some other factors like the size of the facility (the bigger the more "economies of scale" is able to kick in) vacancy/occupancy, & so forth. 

I stopped trying to argue with my peers about it.But what I really want to stress is that a bank appraisal is a bank appraisal designed by the bank, for the banks use.

(You'll note the designation in my profile).

It depends on a lot of factors including "the future" which no one can predict.With that said, when considering if it will cash flow, I would add the rent from one side to the amount I would have to pay to rent elsewhere. 

So vacancy factor will be 6/24= 25%.

The other factor is what price range you are buying in and absorption levels.

Any bills where they can be attached to the house, it is easier if you pay them and factor those costs into the lease. 

That HELOC is, by the way, revolving by design. 

Also be sure to factor in the added costs of having an STR vs a long term rental.