While our deck and railings are secure, I constantly fear someone might do something foolish -- or worse, a child might do something naively -- and fall.What is the best way to help communicate safety to guests, and what are steps I should take to minimize liability should something happen?

When your income starts to increase you may want to look at S-corp, it will help you minimize tax liability (but again, this is later on when your income grows).

The condition of the house is unknown, might need minimal work or major rehab.

Either way, you can minimize the out of pocket.Given your experience flipping, I'd suggest you find a junker to fix up to rent.  

With the HELOC option, the fees are minimal, the money can be deployed and repaid over and over (velocity of money). 

You said the current home is not in your name so you will qualify for FHA on a new purchase of a multi unit, and the down payment will be minimal. 

My plan is to minimize my living expenses and get started in real estate at the same time by purchasing a SFH or small multi-family that I can househack.

I'd start with something that needs no work or minimal work until you have a better idea of what is involved.

I think ~$100 per unit per month is a fair maint budget and another ~$100 per month per unit for CapEx is a decent start for ongoing minimal work. 

If you live in it as your primary residence for at least 2 years during the previous 5 year period, you can get all your profits tax free up to $500k, but if you sell it before 2 years, you will pay tax on your profits.IRS Topic 701VA Loan - difficult to buy a fixer-upper since VA suspended their rehab loan option back in April 2020FHA Loan - doing the 203k with only 3.5% down is a great way to go with minimal out of pocket cost.