For real estate, Set For Life by @Scott Trench is the one I generally recommend as a starter, and give as a gift to friends for their teenage kids.

Out-of-state investment has been easiest now than at any time in the past.

If you're going this route you want to make sure you're the easiest and nicest place to stay or at least in the group of units that they decide to keep.You'll need to address one of the main arguments against STR's which is wear and tear on buildings/community areas.

She is gifting me the HELOC to use towards down payments for future rentals, so I would like the flexibility of only putting 5% down on this first property, if needed.

If my parents were to get a HELOC and gift me the money for me to buy an investment property outright cash would there be any taxation issues?

If she gifts the property to us then we are over the $30k gift allowance for 2021.

Your father is basically gifting part of the home to you.

(I personally think emails are the easiest to ignore)6.

I would need a lender to confirm this but I think she would be able to gift you the down payment.

The single families are the easiest to manage because I find tenants willing to care for the lawns and snow removal.