If I set it up as a 5 unit it will become comercial real estate and then a comercial loan would apply. 

@Tim Jacob, does the 2-unrelated-adults law apply to owner-occupied properties in the county as well?

Specifically applying to Virginia (if it matters)

I'm looking at 5 unit+ properties and adding ADUs since those with immediately be valued off of the NOI.The CA state-wide rules for ADUs don't apply to 5+ properties (meaning, you can only add them to SFR or duplex properties), and I don't know of any City that has alternate rules that are more permissible. 

Do my kids need to apply for EIN, TIN or any other numbers?

However, if it's a Mortgage foreclosure/Sheriff auction then the rules as @Andy Mirza mentions above apply.  

Knowing which comps apply in which situation takes experience in and knowledge of your property type and market. 

That wouldn't really be house hacking, since you can only have a family member living in it, not a general renter, and you also can't pass the unit on to a subsequent owner automatically - they have to apply to the town and be granted it for their family member, separately.

Cash in, cash out.Cash in = your monthly bills, including the mortgage paymentCash out = rentThe higher the spread, the better the market.Negative numbers need not apply.

I give a $300/mo rent credit to apply towards the renters future down payment and I was paid “option consideration” funds of $10k that are non refundable if they do not purchase the home within the next two years.