Lots of talk about this on the Bigger Pockets (real estate website) threads, if you're interested in reading more there.
Most seasoned investors are smart enough to have some solid cash reserves.
We own three units and thankfully, have not been effected. Two of the three units are rented by grad students whose university programs/co-signed parents help subsidize their rent. I was thinking they might opt to move home with the university going online til Fall, but this has not been the case. One set just renewed their lease for another 12 months, which was a relief. We do have cash reserves to pay for all three units empty for a while, but obviously no one wants to run those down if you don't have to.
Our third tenant utilizes a government program for VA veterans, not unlike Section 8. No instability there. It made me glad to have this diversity in our portfolio, since even if the other two units ended up empty, the cashflow from the VA unit could help cover the PITI's on the other two. All of our units kick off good cashflow after saving for CapEx, vacancy, reserves, etc., so we have wiggle room to lower rents in a serious crunch. Pre-pandemic I was hoping to refi one unit we had rehabbed and pull out some cash, but I'll likely leave it be for the time being since bank appraisals are likely to be very conservative.
While I wouldn't wish financial distress on anyone, I am hoping for an opportunity to buy another couple of units in the next 12 - 18 months.