Other random expenses could be included like a portion of your phone, wifi, travel, or other LEGITIMATE expenses related to running your real estate as a whole (and not to specific properties). 

I have a doctor friend out of residency who just purchased a brand new townhouse and is househacking it.

We just bought a new personal residence and got a traditional 20% down mortgage for 30 years.  

We currently own two homes, our main residence has an in-law apartment that we rent out on a short-term basis because we are in a tourist area.

So our primary residence is under my name, our second home (Ocean City Beach House) is under my husband name. 

It turns out to be a 3 year violation notice on the property I did not know about when I purchased this property as my primary residence.

@Ben Boss When you are  buying 1st property as primary residence you don't need landlord experience.

So the question is what are the flaws in the following deal for the owner of a principal residence and the real estate investor?

Only problem I ever heard of was back in the day some condo associations didn’t have enough primary residence owners and the whole complex would be off limits. 

Hi BP,I have a question when you have over $500K in gain when selling your primary residence.