One important detail is that my brother currently lives with us, and we are open to having him stay with us if we do make a purchase as a renter to help cover our mortgage.I see our main options as the following:1) Buying an SFDU to live in, and "house hack" with my brother continuing to live with us and pay rent2) House hacking with MFDU.

If the rent payment covers your mortgage and you have a good tenant, why would you get rid of them to take on the expense of unit turnover, because you will have to do one, and the 5% vacancy loss just to increase your rent $150 per month?

He had this ambitious flip lined up and decided to tap into a 0% business card deal to cover the rehab costs.

This has to cover your debt payments also.3.  

Does he not cover that yet?

Since I am having my prospective tenants cover the cost I would prefer to have the lowest cost option that gives you the most bang for your buck, but at the same time I want to be sure that what I am paying for is reliable.

It was a 1970s property, and when the plumbing needed an overhaul, I found myself scrambling to cover the costs.

My bookkeeping firm provides me with a steady active income, which allows me to keep doing deals, cover unexpected expenses, and navigate the occasional black swan event.

Possible add insurance on your appliances with them paying by adjusting the rent or if they are OK with it so if something else breaks,your covered. 

Even then, all of my booking.com clients are American I offer a 25% discount 0-3 days out. add a 15% fee which essentially covers your commission. set up with one hour to cancel, flexible / strict option but no refund 60 days out or later. sync it with Airbnb and or the other ones you are doing.