@Alexander Spira A taxpayer qualifies as a real estate professional if (1) more than one-half of the personal services the taxpayer performs in trades or businesses during the tax year are in real property trades or businesses in which the taxpayer materially participates, and (2) hours spent providing personal services in real property trades or businesses in which the taxpayer materially participates total more than 750 during the tax year.You have to meet both tests not just satisfy the 750 hours.

He stated that quieting the title can be expensive and he would need a $5,000 retainer just to get started, and that it could take months and potentially cost much more than that. 

Asbestos is similar with the exception of friable materials, like insulation that can turn to powder when disturbed.

Now you could just account for this in your reserves but I doubt anyone properly budgeted for material spikes of 2020/2021(I know I didn't). 

Knowing that aside from new builds, approaches may be limited to materials selection (targeting local and low/zero VOC materials), green cleaning products and potentially incorporating low maintenance landscaping (natives, xeriscaping, polycultures to mimic nature so they don't need regular trimming/maintenance), what else have you seen/used? 

The owner or spouse must be actively materially participating in the management of the property at least 100 hours per year and more than any other person or entity. 

Start writing down or just recording how you want things done, so you have them as training materials for your hires.- Also, figure out the order of what you want to hire & delegate.

Now those for the material can be very thorough.  

Tearing down a property usually requires a permit and inspection for dangerous materials (lead, asbestos) and could increase costs of demo.You might see who is going to take the property, if it's a local bank you might pick up the note by assuming it, (they would just make a new loan for the amount owed and do a sale between you and the neighbor).

You buy raw materials (junky houses and building materials).