They mentioned the custodian is who will be on the lease (I am not sure if the tenant will also be there, seems that the custodian acts as the guardian in this case) and that they are the ones who pay the rent.

Quote from @Patrick Roberts: In short, no.

The market supply has had a surplus meaning they are sitting longer and "stockpiling", nothing crazy but it is noticeable in the chart.

One person I know has a house in PA, CA, and TX. 

@Jonathan ChanDavid Greene's The One Brokerage will do HELOCs on investment properties.Not affiliated, have worked with them in the past.

In the meantime, tell her you are done talking to her about the heat.

Do they have a lot of repairs called in?

From my observation/experience, Berryessa and Piedmont Hills areas are more family-oriented, so the demand there is generally for primary residences, renters, or travelers visiting families.

-investing in rental properties and STRs?

In Mexico, as you know, when you rent to visitors, you generally don't do LTR.