I don't have as many units as your family member manages but I still have three digits worth. I allowed extra time for people to pay April's rent. I ultimately had one family that could only do a partial payment and another that paid nothing (but there was issues there prior to covid), everyone else paid in full. I think it comes down to unit class and type. An F-C class building might have a hard time collecting at the best of times, and this is not the best of times. Stimulus money won't go out to folks without social security numbers, and not even folks with ITINs so depending on the tenants it could be extra tough. Generally speaking these properties get higher rents in proportion to unit cost so it COULD be factored into the purchase if the owner didn't spend every last penny to buy the building (and carrying costs of course). This is going to hurt owners in the long run in a variety of ways even beyond rent collection, but it will also crush a lot of people credit assuming the owner leverages their power to try to collect. Outside of rent collection I postponed rent increases that were to take effect April 1st, I am not sending out new increases as I normally would, I had a recent vacancy that took three weeks to fill which normally fills in the first week and the only way I got it filled was to discount the rent when I finally found someone well qualified.
I would not expect to recover most of the outstanding rent for that owner, but I would expect to be able to collect some. If the tenant is choosing to destroy their credit in exchange for a few months without a rent payment then it appears they will pull it off. If they don't have a SSN or an ITIN then they may not have a credit file to destroy!
Not a situation I would want to find myself in!