At the same time, I like the idea of a beautiful programmable t-stat.The heat is supplied by a brand new furnace.

I'd estimate your cash flow after you pay the loan payment would be $600-$800, which a lender that understands investment real estate should give you some credit for on your DTI.As for a bank, I have a specific lender at NBI that I would recommend.That 600-800 you are factoring in the HELOC repayment each month too, correct?  

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23If a purchase, you also generally need reserves / savings to show you have 3-6 month payments of PITIA (principal / interest (mortgage payment), property taxes and insurance and HOA (if applicable).

Compounding on one another sure that will have a big impact on the market but there are a lot of factors at play.

What factors should I consider when setting rent per room?

Utter blasphemy, only "unsophisticated" investors buy in cash.An experienced investor once told me "why use my cash, when I could just default on OPM" I know its not popular thought on BP.. and of course ramp up requires it unless you inherit a ton of dough but as we age out I sure like free and clear and no debt.. just the hassle factor of having to make payments :)

Credit is a factor as bad credit may limit options, or may have the lender require you to put 10 or 20 years of taxes and insurance into escrow. 

When under contract at 300k with the expectation that codes would be the determining factor on what can be done on with the property, as it relates to new construction.

When under contract at 300k with the expectation that codes would be the determining factor on what can be done on with the property, as it relates to new construction.

This property will require a pool to fully optimize its earning potential, and I've already factored that into my calculations.