Be aware of this: $1.5 mil is not that much if you live another 30 years (age 89).

They also purchased a window-unit air conditioner (the house has central air conditioning already) which my dad saw when doing yard work; otherwise, we were not made aware of this addition.My question is whether or not it makes sense to make an addendum to the lease, stating that we will cover upwards of $100 (for example) for the electric bill, and the remainder will be added on to their next month's rent.

Know tenant laws and rights in CA before you acquire a nightmare tenant that is aware of the liberal loop holes.

However, you better be aware of the property tax, like 5% of sales price. 

What should I be aware of when doing this?

@Mike Perez I'm in CA myself so I'm well aware of the problems you're having finding anything to cash flow.

Are there any places that sell single family houses for 50k that’s not in a war zone? 

I am aware of the CARES Act but with the State banning eviction till Aug 20th does that complicate things? 

One consideration I'm aware of is what class the neighborhood is.

But what are the things I should be aware of when writing those articles?