Also, the opportunity cost of leaving the property vacant for a year while paying a mortgage on it and not receiving rental income is much higher than what the marginal difference in rate will cost you until you cashout refi it.

there are costs to close on the buy, costs to hold, costs to finance, and then MAJOR costs to sell, plus...

Folks tend to far underestimate the cost, and length of time, that it takes to rebuild from a disaster such as this.

BTW, PV is currently hawking a "we partner with you" scheme that will cost $9500!

Cost to build should not matter there.Look at your deals. 

The addition would cost me about $80k to convert the garage space into an additional unit.

That's $18,000 a month income and their costs are probably 1/3 that.

But if I've marked those up by 30% then it only costs $1400 to fulfill.

NOW THE DOWN SIDE OF SHIPPUNG SOMETHING SO MASSIVE AND HEAVY IS GOING TO COST AROUND $6K TO $10K.

It is very time consuming to allocate overhead costs such as automobile, cell phone, etc. to each property.