There's tons of options for legalizing an unpermitted unit or leaving it as it is, so I'd recommend exercising caution, rather than avoiding unpermitted work all-together.If you're buying a true multifamily, one benefit of house hacking is the ability to put 3.5% down on a FHA loan- this can push your cash-on-cash return through the roof, and you only need to live in the property for a year to qualify for an owner occupant (low down payment loan).If you end up househacking a SFH with or without an ADU you can get better loan terms going conventional, with a 5% downpayment. 

I believe financial gain has similarities to exercise.