I’m curious: are others who house hack buying homes they can just barely afford, or are you sticking closer to the ~30% housing rule and using house hacking income as an added bonus?

I believe that's their primary business model.Seems like this would be a great bonus! 

A good real estate accountant can save you thousands of dollars by leveraging entity selection and formation, tax deductions, cost segregations, bonus depreciation and tax planning.I recommend finding an accountant who specializes in real estate taxation, business taxation, financial planning and tax planning.You may want to consider working with your accountant remotely to expand your options.I would also recommend looking for a accountant willing to work with you throughout the year.

The more common one is a flat value for the ADU, like they would for a pool or another bonus.

The landlord should be named on the tenant's insurance policy for additional protection and to assist with tracking compliance.

I am also a huge fan of real estate and for the past 50 years there's been a way to combine both.By leveraging a Self-Directed IRA, real estate investors enjoy both the traditional advantages of property ownership and the additional tax benefits of retirement accounts, creating a powerful wealth-building strategy.

I really would like an app or site that allows you to compile a list of properties with notes on the spot, and bonus points if it pulls up any info on the property as well. 

I am considering building up on my fourplex. 2 additional units.

Ok it might not be 1:1 but it will add additional revenue.

If you sell a property, and do a 1031 exchange with the proceeds, but don't need all the proceeds for the down payment of the next property, are you taxed on the additional profit that isn't part of the exchange?