Congress just approved $2 billion worth of rent relief for landlords that will go to previously owed rents too.

—An heir would first have to have the authority to sell the property which usually requires probate—what advantage is there to the heir as they have no liability for the debt?

I was just made an authorized user on my parents card so I can start building credit

If you wanted to go this route.If you want to keep your tenant, have them sign an agreement not to have the named subject at the property and anyone else not authorized on the lease or section 8.

If the dad is solely responsible for the rent payment and if you don't want to redo the lease completely, she could be added as an authorized occupant.

I note below giving long notices, but there is a chance that any additional stimulus coming through congress may have more stringent moratorium tied to it, so there is a bit of urgency.Assuming you are going to be upgrading units, I would give one tenant notice at a time, with ample notice.  

Later that evening my wife noticed they had a total of 8 people at the house around 8pm, she sent them a message reminding them of the covid rules as well as our #1 house rule stating "Any un-authorized guests on the premises will force the cancelation of the booking immediately".

So find your market which you know like the back of your hand or have friends/family/colleagues who know a market and start looking there.If you're going out of state I recommend reading the Long Distance Real Estate Investing book by David Greene and identifying a market with this spreadsheet (FYI I'm not the author, but found it very useful!).

Happy to see the Stimulus Bill currently in Congress will have Renters relief.

@Iqbal Zaveri  The law is clear on this and the Housing Authority is correct.  90 days notice is required when terminating the tenancy (or failing to renew the lease) of a Section 8 tenant in California.