You may consider posting your question on Bigger Pockets forums (the RE website). There is a higher likelihood of responses there.
FWIW, we are not yet retired but have used a HELOC to purchase rentals. Most investors who use this strategy use the HELOC to buy a (fixer upper) property in cash, improve its value with a rehab, and then refinance it to pull the cash back out. The rehab/improved value, if calculated correctly at the outset, provides enough equity to leave in the deal to satisfy the banks requirements (aka, the BRRRR - buy, renovate, rent, refinance, repeat). I would think being retired wouldn't necessarily effect your ability to refinance in this situation - esp if you're working with a lender who calculates the rental income against the 'debt' of the new mortgage.
IE, lets say you use your HELOC to buy a property with cash at $100k in an area that generally commands $130-$150k for 3/2 SFH's. You put another $15k into the property in a rehab. Rent out the property at $1400/mo, and then refinance with a local credit union who accounts for the rental income. The bank usually wants you to leave 25% equity in the deal, but thanks to your rehab, your property is now worth $150k. You refinance leaving 25% equity in, and set up a new mortgage on the property for $112,500 (pulling that cash out to pay off the majority of your HELOC and rehab, save a few thousand here or there). Then your rental income is accounting for PITI + vacancies/repairs/capEx, etc. And you're ready to repeat the process, if desired.
These are obviously back of the napkin numbers, but that's the idea. In my opinion, its the smartest way to use a HELOC because you're only drawing down the funds for ~6 months at a time.
I will have to humbly disagree with rothwem's perspective that all $100k cashflowing properties are in "war zones". We live in a M-HCOL area (Austin) and purchase our rentals in another market (200k - 300k sized college town with multiple economic drivers and predicted growth). We regularly see deals of 3/2 SFH's for around the $100-$115k mark that work to cashflow or add value using the BRRRR method and are in solid B+ areas. We purchased two such deals in November and December 2019. If your particular market isn't great for cashflow, you'll have to assess whether you're comfortable investing in real estate elsewhere.