Personally, my strategy (in the midwest) has changed over the past few years and BRRRR hasn't been the go-to approach as much.

During the slow season, do you personally focus on getting more rentals, focus more on family/personal life, or do you do something else?

You'll come out on top no doubt.

HELOCs are generally provided to properties that are held in the owner's personal name.Are your family members not interested in refinancing the property?

I'm in Kansas City so I can't say for sure but I would highly doubt they'd raise any alarm bells.

My wife and I have overhauled our personal budget to reflect the 'pay yourself first' approach (allocate in order: income comes in -> invest -> donate -> fixed expenses -> variable expenses -> fun $$).We are looking to see what experienced people generally recommend for a holding tank for that 'invest' allocation while we target our first real estate deal.What financial vehicles have you guys used that works well for this?

What appears to be great "curb appeal" to one person might be overwhelming to another. 

Haven’t used it personally but a good friend of mine who self manages around 20 doors uses it and swears by it. 

Insurance liability, I personally know 2 families that lost their children in home pools.

While Facebook Marketplace isn't the sketchiest site (craigslist), I personally would never give my ID across it.