We bought a house last summer, and ended up buying it outright. There are options to qualify for mortgages based on assets, but it is, of course, not the most common way to go about it. Unfortunately, every lender I contacted had halted asset-backed qualification last year, due to nervousness about the stock market through the pandemic.
I have not tried to go back and get a mortgage, which would be classified as a cash-out refinance, even though there is nothing to refinance, because it is our existing home.
We end up generating "enough" cap gains through managing our individual stock portfolio. If I was faced with a situation where I should sell my investments (the company took a turn for the worse; the market price is way above what I think the value is, etc.) then I would sell, and not let the ACA tail wag the investment dog. Loss of subsidies would be a cost of doing business, but if you are talking that much, then it's still the lesser cost, vs. The risk of the investment loss.
In the case of a rental business, I would think that would be similar: the lifetime value of a rental is more than any year's subsidy, so losing out on the ability to make the investment is likely a higher cost. But how likely are you to get into rentals? If this is still a matter of exploration or daydreaming, then you are giving up a certain benefit for an unlikely gain. If you already have an active portfolio and you are preparing for a likely wave of foreclosures, then it might be a prudent move to prepare, specifically for this year and the next.