We do not drain our hot tub after every guest, but we do test and adjust the chemicals, vacuum it (sand) and skim the top if needed after every guest. 

If I were you, I'd go for the heat treatment as long as it's immediate and kills eggs too, because chemicals need to be reapplied. 

I have learned to get a cheap maintenance person and have them buy the good chemicals from A1 Able and spray it for you.

I used to work for a start up, we sold maintenance software to big oil and gas, chemical companies and other big producers.

That includes weekly cleaning, chemicals, flushing of filter when it needs it, topping off the pool, and my people clean the pool deck when it needs it.

I would put some of that in non synthetic ETFs and have it in the stock market.

Often times that expense synthetically wipes out positive cash flow while you own the property.

Look at the topography and terrain to determine how.Evaluate fundamental infrastructure and service availability, as well as expose examples like wetlands and flood zones, protected lands, hazardous chemicals etc.

Everything I read online says DO NOT use exterior stain on the interior due to the fact it gives off harmful chemicals. 

You will get efficiencies of scale with chemicals and service calls.