Refi primary residence to turn into long term rental?

[Andrew Everett]

Hi BP - 
My primary residence is currently on year 3 of a 15yr mortgage at 3.125%. I'm looking to buy my next home which will be a non home sale contingent purchase. My question is whether it makes sense to refinance my current home on a 30yr at 4.5-4.75% (as an investor + rates are ticking up) in order to cash flow as a long term rental. Is that additional interest really worth it over the life of the loan, just to get cash flow? On the flip side, I've always been taught to never have negative cash flow. Am I thinking straight? I'm between these scenarios:

1. Rent as-is with current 15yr owner occupant loan -- estimate negative cash flow

2. Rent unit with refinanced 30yr investor loan -- estimate decent positive cash flow

3. Sell property and deploy equity elsewhere -- have future investing goals of mult-fam buy and hold

Thanks!