I'd tell them you will buy it and install it, however, their rent will be increased $X a month to cover the fact that you've now supplied a washer and dryer. 

Not with all the supply and labor shortages going on. 

The question is how is the profile of the state in regards to landlords, growth for the economy, supply of land, and is this house attractive enough on the exit to garner an aggressive bid if you were to sell in the next up market cycle in 7, 12, 15, 21 or whatever years?

Real estate is a complex asset class due to the lengthy process of increasing supply.

Our response stressed that we take great care of the pool with weekly maintenance, that they enjoyed having the temperature in the high 90s, and we are glad they liked all of our pool and beach supplies, etc.  

We have a major supply issue in Sacramento, and more and more demand for housing.

I always wonder because the more people say an area is great to invest in, it seems it will drive up supply of houses.

Stop hanging out with your deadbeat buddies that spend all day drinking, talking sports, and otherwise wasting away.

Utilities, taxes (property, local vacation, & income), landscaping, furnishing / decorations / amenities, pest control, & supplies (soap, TP, etc) are the big ones on my STR calculator that you didn't mention.I'd also recommend using the enemy method to determine expected income.

As long as there is a good thesis as to why the demand will remain high for shorter stay rentals  and most importantly (1) the use is allowed, (2) the use requirements are protected by in place permitting and licensing and (3) the permissions are transferable through a sale you will be on the right side of the supply/ demand equation.