CV2.. I’m in the mortgage biz, so can give you all kinds of ideas about financing options, but I’ll hedge on the tax advice.
You can talk to your CPA, but if you can paper trail the funds and what they are being used for, you may still be able to take the direct deduction, otherwise you may still be able to deduct the HELOC interest with the same net result.
I’m not sure how many people have rentals with 30 YR fixed loans below 6%, but very few.
Without knowing how much equity you have,don’t fret over others with lower rates. If I knew more about your situation, I might be able to suggest some other creative ways to increase your cash flow, but having equity and a 7% loan is better than being upside down with a 6% loan!