Additionally, I'd appreciate any tips on balancing cost-effectiveness with durability.

Rent costs are nearing 2019 levels.

Airdna has years' worth of actual data, so there's a reason it's costs a bit.

We need to know the details of what they were installing, the location, the cost of materials, etc.

All I can imagine is a lot of blight hitting many rental units when the costs to maintain rise beyond the capacity to finance that maintenance.  

Aside from seeing a parcel and knowing a great project could be built on it, it's necessary to be able to show precisely what can be built, how much it will cost, and have real numbers, based on actual bids to back up your projections. 

I do like the smaller homes because they are brand new and maintenance costs will be lower.

Such a fantastic book, FHA financing is a highly effective house hack and can be combined with a sellers concession or up to 3% with 3.5% down to reduce or completely cover closing costs.

We were able to get seller credit to help off-set the cost, but now we have heard of some people getting a free roof with the installation of solar.

I believe your cost basis will increase to the day you take ownership vs. waiting until he passes.