Use a HELOC or Cash for new HVAC unit?

[Jeff Duford]

I just bought a rental property that needed a new HVAC system. Total cost for new unit (and AC) is $6500. I could pay that from cash in my checking account, or... I could use a HELOC from my primary residence.

I'm curious if anyone has an opinion, from a tax perspective, which is the better route? If I use the HELOC, I can deduct it (with new tax law i wouldn't be able to deduct HELOC if used on my own residence so maybe this is a good use for it), but if i pay cash then clearly i don't hurt my cash flow quite as much....