This is exactly what I've been saying forever - that lenders LOVE people who are prepared with math!

Oh, and one last thing: if you don't plan to live there forever, and you don't think the market itself makes a good buy-and-hold market, remember to count principle paydown and look at your profit over a long (10-20yr) time period.

I have a 210K interest only HELOC untapped with a $0 balance and a rate @ 3.75 and I'm looking to do a refinance on some of my other properties and wanted to get a sense of how that would factor in to my DTI. 

That's a matter of long term strategy to avoid ever increasing insurance rates due to hurricane risk factors.  

Based on the BP Calc, I can make $40k with nearly all holding costs factored in if I buy at $330k.The comps on the high side are $600k and up and all have 4-6 bds.

Normal real estate appreciation, the kind agents and homeowners talk about, is dependent on a lot of factors.

Factoring in for weather (something we don't have in socal) Is a necessary step in the due diligence Nevertheless, for my long term landlording goals, I do believe that this will work.Thank you.

Another factor is what you are willing/able to manage.

i do shorter amms because i want them paid off, and keep the cash flow, its one thing if you want 100+ properties, but 15- 20 paid for ones gives me an easy 6 figure income forever, and ever, and my kids lives and their kids lives if managed properly. pay alittle more now for the flexibility, and get them paid off, so what if you have to re-up in 3-5 years, interest rates wont be 10% then, and if they are inflation will drive your rents to cover it anyway, inflation is great in real estate, it means your property will be worth more,  but the purchase price was pre inflation.

-contact local landlords and get their feeling of the interaction (easy, heavy handed, not at all, waiting forever) with the local HA; also for the quality of the available local section 8 tenants- i would look for tenants previously long-term in their former place; then you educate them/train them to your requirementscontinuous success