If you're considering a significant investment in smart locks, I strongly recommend exploring alternative options that prioritize both convenience and reliability.

We do the whole place in the same material (these are all apartments) and people love it, just like if someone put hardwood through the whole house. 

I checked out neighborhoodscout.com but I am wondering what good competitors are out there, and if there are any free (or lower cost) alternatives.

Alternatively, if you're able to put a good chunk down payment on a property and the rent(s) cover your mortgage + expenses + a touch more, in an area that you like and know will appreciate, that's pretty nice as well. 

Are there alternative/better financing options for this plan? 

GPs do not like to put material portions of their net worth into deals.

Question 1: Does $4698 for materials and labor to prepare my house for a hot tub seem in line?

I was able to negotiate a package that included the land, some of the materials, and the permits to build it.

When you have a big cost segregation depreciation plus your big startup expenses such as furniture and supplies, and you then have a big tax deduction against your big W-2 income because your passive losses are no longer limited with your big material participation, it increases your audit risk a ton.

No, material costs sit nearly identical.