Our case is a bit different, but briefly, yes I think using a HELOC is usually a good idea.
If we find the right property we plan to use all of our HELOC to finance it.
We may even need to use the HELOC from 2 properties if the rental property is over $400K.
This can allow for a competitive offer with no subject to financing.
We will then roll the HELOC into a mortgage on our residence (Kind of scary.) to get the best rate.
The income from the multi-plex will be enough to cover all expenses & debt servicing.
The multi-plex will be mortgage free. The reason for this is because the rate on multi-plex is about 2% higher than a single family home.
From our experience getting a commercial multi-plex mtg is a pain in the ass.
Honestly, we tried & with all the environment inspection hoops to jump through you may loose the deal before you can close. (Obviously not impossible but more challenging than getting a house.)
I can't recommend anywhere to borrow. (BTW I'm in Canada & I think our banks lend with more conservative rules.)
We may need to use some cash for closing costs but do not plan on using a lot. ~5%
On paper, putting zero down gives you an infinite ROI.
But don't get too excited. ;)
Regardless of where you borrow, be sure you have a positive cash flow when considering every expense & maintance & vacancy & debt servicing & a 5% management fee (even if you do it yourself).
By not having cash down, it will just make the positive cash flow requirement that much more challenging.