How to run numbers for house hacking a SFH with roommates?

[Jeff Lundeen]

My current market appears that I am best suited to purchase a 4+ BR SFH and rent out the other rooms for my first deal. I'm curious if using this strategy how the numbers would differ from house hacking a multi unit or owning a rental. What I'm looking for is an ideal % or rule of thumb on how much of the mortgage my roommates/tenants would need to pay. Obviously over 100% would be ideal so that I would live for free and could put aside extra money for unexpected expenses. But if getting over 100% isn't possible, is there a heuristic for what I should be getting to make the numbers work?

Let's use some numbers to make this easier for me to grasp:

If the mortgage payment is $2,000 (including P/I, taxes, insurance, and PMI if applicable) on a 4BR. If I choose to occupy one BR and rent out the other 3. Charging $700 per room puts me at $2,100/month in rental revenue. $100 over my mortgage, but not accounting for other expenses. It allows me to live for free, so I could put aside what my current rent is to save for expenses. These numbers put my collected rent at 105% of the mortage. Is that enough when setting aside money for capital expenditures, vacancy, and other unforeseen costs? I don't see much talk about the benefit of simply putting my rent towards equity and how that will help me for future deals. I know the experience I would gain of being the landlord and co-living with my tenants would be valuable.

Next, lets run the same example at $600 per room.  That puts monthly rental revenue at $1800 which is 90% of my mortgage.  Now $200 of my portion of rent that I am setting aside goes to the mortgage.  The remaining money that I am setting aside from my current rent payment ($600) would be $400 and that would be to develop cash reserves for expenses.  Is this enough?

What about if my monthly rental revenue was 80%?  Meaning I would collect $1600 per month and be responsible for the remaining $400 to the mortgage, having only a $200/month allocation to reserves.  It's not quite $200 in cash flow because these numbers don't adequately budget for Cap Ex, vacancy, and anything else that I am forgetting.

I've listed 3 different examples of % of rental revenue in relation to my mortgage: 105%, 90%, and 80%.  There are obviously many other possibilities for what % I can charge.  My main question is at what % do the numbers seem to work?

Please help me figure out what other questions I'm not asking that I should be, or things I should consider that I may have left out.  Is this even an accurate way to think about how much rent I need to charge?