The floor joists were broken (2"x8"s on a 16 foot span...).

That’s great you were able to take advantage and you’re setting yourself up on a good footing.  

Plus I feel like on some cosmic level you need to step foot at least once where you are buying.

I am in the suburbs of Chicago and mostly interested in the Joliet area.So as a new person who is literally putting one foot in the door, looking back, if you were me...at this moment...what is the one thing you would have told yourself; or done differently?

We have bought houses that we never seen the property and have yet step foot inside them.

My thought it re-parging that 40 foot section of wall might help limit the smoke but that seems like a substantial expense for an issue like this and likely won't completely solve the problem.Does anyone have experience with alternatives for minimizing smoke?

I'm thinking there could be a 4 by 4 foot cubby built somewhere along the front that is unlocked until a package is delivered. 

As already mentioned above, if you go the amazon route you will have to be nimble to keep up with the latest fad sales or whatever as fads are really the only way to get a foot in the door (vs. trying to sell a staple).

Option 1: a 400 square foot 'tiny home'.

I would like start off on the right foot and treat this like a business, as I plan to add more rentals in the future.