The picture they used was more of a B or C market location.  

In your case looking to larger assets where you can effeciently cost segregate to gather bonus depreciation would be a smart move.Appreciation - Where in the country is the asset class you like growing or going to be growingAmortization of the loan - What sector or even region if you look locally for funding, is going to offer the most favorable lending so that less goes to interest expense and more to pay down of principle.Have fun with a spread sheet comparing these 4 returns from your investment with the type and location of assets you find attractive. 

It is be difficult to answer in details on a post but I will give you some general info here as a guide:- The legal limit will depend on your location, layout of your house, and parking availability.

Hello everyone, I am located in New York City (Bronx), and I am currently tackling a renovation for a triplex rental I plan to keep.

Good properties/locations will see values and rents grow at a greater rate.

Location?

I'm located near Great Falls in central Montana.I have been self-employed for about 4 years and love what I do, so my goal is to build total wealth long-term, not to maximize cash flow for FIRE/financial freedom in the near-term.

I suggest you talk to a real estate transactional attorney licensed in the state where the property is located and get their advice on your options. 

Now if you want to buy and live there forever or you want a specific location or lifestyle or the amenities, might be something to consider, but not for investment....they're for living.Your best option right now depending on your income, is probably to buy at least 4bed house or 5 bedroom if you can make it work financially and rent bedrooms. 

They do this in a lot of locations.