im in Orange County CA and there is a huge market here for room by room rentals here. i've been doing this for quite some time (over a decade now), and it certainly has its pro's and cons. my advice if you go about this is make sure you do proper vetting before moving someone in... not only for financials/ credit-worthiness, but also for temperament and expectations in a co-living space. we ask a lot of questions like "how do you handle conflict?"

@Dillon Clark-don't pay extra down on your mortgage-don't use a HELOC-save up as much as you can-hope this helps

So they are good paying retail.. we had 5 to 7 offers on each project .

Furthermore if they are always paying they probably will stiff you in the end if they know they aren't going to get the deposit back. 

It's worth paying a premium for the brick buildings that were built for multifamily.

I know what it’s like to be in your position, and I believe in paying it forward.

@Helena Lee, I do not have experience with it, BUT I would expect to pay capital gains on the bitcoin. 

The rental income from the first home will pay for the mortgage/monthly costs.  

So I did not pay extra for it, but chose it anyway over other places.

The loan on this house is $1,200,000.I moved in to my new primary residence by the end of the month.Starting July, my original primary residence was available as a rental and was being shown to prospective tenants.My new tenants signed a lease that began a couple weeks after showing, in July.To calculate my primary residence mortgage interest deductions, i'm using the following formula:650,000 / 2 = $325000 loan from January to June1,200,000 / 2 = $600,000 loan from July to December$750,000 limit / (600,000+325000 total loan value)  = 0.81 multiplier(0.81 * $X first house interest) + (0.81 * $Y second house) = total interest payed i can deduct from my primary residencedoes this look correct?