HELOC or refinance right path?

[Jacob Bremer]

I bought a rental in 1/2021 for 700K. Principal is about 615K right now. Rate is 3.4 conventional. Monthly payment is 4,050. Overall, I'm just barely cash flowing on it. The current market value of my home is 900K. I have some great opportunities to for additional rentals in my area and was wondering if potentially doing HELOC to try and leverage it to secure an additional rental.

Additionally, I spoke with my lender and he said I could refinance the property and bring my monthly payment down roughly 3,450/mo. Of course, it would be a higher interest rate, but as a rental, wouldn't it make sense to do that? 

I realize these are both different, but curious if I'm missing something I should be considering, Seeking a little advice on both fronts.