Which house as collateral for mortgage?

Many folks here have asked the question which collateral asset they should use to secure mortgage loans, their primary home their investment home?

The fact financially sophisticated investors on TZLC forum are asking this question puzzles me. Separating funds financed from investment property vs. owner occupied home is largely mental:

1. a dollar is a dollar. money is fungible. it does not know where it comes from.
2. always borrow from the lowest cost of capital first and resort to higher cost of credit when low cost borrow capacity is exhausted.
3. view your whole asset and liability as a portfolio and manage your leverage accordingly.

To me it is a pure arbitrage opportunity. I would just get a HELOC, which has lower or zero refinancing cost. 

Having said all these, you are lucky that you have a choice. Most of the landlords here do not have borrowing capacity of any sorts.

just my 2c