Have you seen a housing market like this before, and how did investors keep growing revenue in past difficult periods?

Not quite. The closest comparison is the run-up to 2007, and the financing underneath is the big difference. Between us we've spent decades in lending and real estate. Ahead of the last crash, a lot of owners held adjustable-rate loans that reset higher and forced sales. When most owners instead hold low fixed rates, they simply don't want to sell and give up that rate, so the market tends to seize up on low inventory rather than flood with distressed listings. As for how investors kept growing revenue through hard stretches, the oldest lever is raising rents on existing units. Beyond that, the real deals rarely sit on the MLS. They come from motivated sellers, and the classic drivers still hold: death, divorce, debt, relocation, and vacant or long-sitting properties. Subject-to, meaning taking over a seller's existing financing, is one tool in that kit, and plenty of other investors are hunting the same deals with it. There's no reliable trick here. The work is sourcing motivated sellers and running numbers that still cash flow, and nobody can promise which way the broader market moves from here.