All else being equal, a smaller unit will sell for a higher amount per sq fit than a larger unit.

Finally, Home depot, Lowes, Lumber liquidators... where do you shop for good savings and good quality products?

I would feel very comfortable if I had $7,500 reserved owning a duplex incase I ran into a major maintenance issue or larger unit turn. 

Hopefully earning equity on the rehabs along the way, so I would be using a smaller and smaller portion of the heloc over time(or being able to go for larger duplex/multi fam properties)...Does this make sense?

It's much easier and looks less suspicious to pay 1 plumber a larger bill instead of 3 different plumbers. 

For now I'm looking at all the creative tools to make my first BRRRR easier/ safer as a first investment, and to have a larger cash rehab budget.

If you have experience and can perform just as good and quickly as a larger snow removal company, then you should do it.

If Covid does not go away and this next stimulus is not as effective as we need it to be, what is some insight on a POTENTIAL larger scale eviction?

After these two duplexes were purchased I was able to move out of the larger one and cash flow my single family residences mortgage payment.

you need a relationship with a local commerical bank.. there are some larger private HML that specilize in this.but they are far and few between..