Austin's first 'Tesla Solar' neighborhood explainedPanels, batteries coming to new homes in Easton Park master planned communityThe Article reports on a new partnership between Tesla Energy, Brookfeild Asset Management and Dacra.

Filters, refrigerator filters, batteries for smoke detectors and fan remotes, light bulbs, etc.Your list is pretty thorough though, I'd only add to make sure you're doing a semi-annual HVAC maintenance.

This is pure luck and definitely not always the case.

Trail cameras are wireless, use batteries and are internet free (operate on data plans).

That assumption is based purely off of Zillow's estimate so who really knows, but in any case,- Would it be wise to go ahead and obtain a HELOC on the property even if I don't plan on using it for awhile?

Only things I can think of are HVAC filters (tenant every 3-6 months), batteries in smoke alarm (tenant twice a year). 

Speaking purely from the standpoint of you qualifying for another mortgage, you at least need to charge enough to reduce your debt burden and get your DTI ratio below say 50%. 

Then ask what it's worth for them.There's no time for them to accrue any meaningful amount in that time span if charging purely interest. 

For context, it's a $700-800k 2-unit MF, which I'm indifferent about in terms of going the owner-occupied vs pure investment route.

This post is purely opinion based although I suppose some may have experience with this.