Not knocking what @Duane Richards is saying here but rather than apply a blanket occupancy rate as a rule of thumb you really need to evaluate the area.

Lack of maintenance was the ultimate issue, we simply could not apply the attention the house needed.

What is the income, or would it be if leased / apply a market cap rate.

Even if you could get it, you would have to hold on to the home for five years before becoming eligible to apply.

I plan on taking that knowledge and applying it to my future rental properties (apartment buildings).

When you leave the house leave it clean, trimmed, tidy to set the expectations high.I bought and mailed my tenants a years worth of air filters to replace and root killer for the sewage line.

Examine it to apply to a local market, and modify it so success is repeatable. 

Does HELOC get treated negatively in any way from lenders when I apply for a new loan?

Happy to say I came across multiple lenders who offer HELOCs on rentals and I’m just over a week removed from applying for one through PenFed.  

Just a reminder that this only applies if you meet certain criteria; basically that you need the money because you were affected by Covid in ways that they list on the IRS website.