. :)) Recently I saw a CL add in my area that MFH owner was selling one unit of a duplex , so the question ; if I personaly own let’s say a fourplex or that might be owned by my LLC , can I sell one or two units to other people and keep the rest ?

That could serve as a POF, for say a downpayment amount.  

Call me a negative Nancy, but if something goes wrong-say a break in and you were the last one to leave the apartment-who's insurance covers it-the tenants or yours? 

I would say as a take away for anyone debating working on without a permit or purchasing a property with un-permitted work, this circumstance is not ordinary.  

It's possible that if you ask her what she would need from you in order to move out early, in person, she'll say a number less than what you're prepared to spend.

She understands that she will not be keeping the property since she cannot recover from the passed due payments, but she has been back to work for some time and wants to know if there was anything we could do to keep her in the home as say a renter since her income is quite good and she was behind due to medical issues. 

@Johnny Corbett Generally the cash flow from multi family properties will allow for a greater return simply because of the efficiency and costs associated with purchasing say a duplex vs a sfr (obvious variables simplified).

All this to say, a voluntary vacancy in January is filled with temptation to either lower one's standards or pay a high price in utility bills, insurance premiums and potentially emergency repairs. 

You also might be able to get a management company to work a deal for say a flat monthly payment in this example say $100 flat fee per month. 

So I have a SF house that we will have owned (and lived in) for two years here fairly shortly.IF after 2 years of living in it, we tear the house down, scrape it, rebuild on the same lot and sell it for say a 400K gain, is the gain taxable?