Astronomically high housing prices but it's also an incredibly popular tourist destination so I'd imagine that the short term rental market would have to be the market to go after in Hawaii.

Brewerytown caught my eye as it is close to center city and in the lower part, it seems like there is less crime and gaining popularity.  

Scaling, I really like the thought of BRRRR but I wonder what other popular methods of scaling are being used?

Here are a few popular options:Zillow: Zillow provides real estate market trends and data, including information on rental rates, property values, and other key metrics for various neighborhoods, cities, and states.Rentometer: Rentometer is a rental market analysis tool that provides rental rate comparisons for specific properties and neighborhoods based on real-time data.RentCafe: RentCafe provides rental market data and insights, including information on average rental rates, occupancy rates, and other key metrics for various neighborhoods, cities, and states.Yardi Matrix: Yardi Matrix is a commercial real estate research tool that provides market insights and data on various aspects of the real estate market, including rental trends and property performance data.It's important to note that while these resources provide valuable data and insights, it's also important to physically inspect the properties and consider local market conditions and factors unique to each location.

One bedroom units are very popular and easy to keep rented to single people and/or couples, because they are usually a relatively low cost housing option.

DSCR is a more popular option since you do not need a job/employment. 

One of the most popular questions I get related to the BRRR is… Do I need to remodel the entire property to refinance my money out.?.

I think demand is determined by the popularity of the area where your rentals are located.

"Build to rent" is growing in popularity and with good reason as supply chain issues start to abate and building costs/sq ft still well below sale price/sq ft in many areas. 

Alex Markle it's probably not a popular option, but what about waiting until you save enough for a downpayment?