I don't have an answer, but now I'm following this.

This measure is designed to shield existing homeowners from the rapid increases in property tax bills that have become a pressing concern.

Bigger renovations like this aren’t our strength.

All this adds up so some serious deductions.

We used a HELOC on our primary to purchase and begin renovations on a duplex nearby, and just this month closed on a fourplex that has a couple units rented, and a couple that need full demo/flip (which is now in progress).I'm taking some big swings and really having a blast doing it.

I wonder whether expert can confirm this?

If you want to stay in your house, then your only option would be to leverage equity which will probably be in the 8-10% interest rate range.Not knowing the entire situation, I think you could consider downsizing and then using the proceeds to buy a 2-4 unit property and start making $40-75K right away with still no debt. 

One of our residents was robbed outside of this property and we ended up paying for the resident to move out and sold this property.

A duplex is a great way to start because that renter will help with your monthly out of pocket costs and it's a convenient way to get into real estate investing.

Quote from @Mario MoralesMorales: what if he got a HELOC, used the funds to get a property, then cashout-refi the new property and pay off the heloc?