How to determine down payment vs loan amount?

Hi,

I have a ROTH IRA account that is valued around $270,000, with cost basis amount  $140,000. As I understand, I can withdraw from my Roth IRA, penalty free (I am in mid 40's), if I don't withdraw more than the cost basis (contribution).

 

My wife and I are planning to buy a home in Moscow, Russia, and I am trying to figure out, what amount of this Roth IRA cost basis I should use, versus taking out a loan.  In Moscow, if we put down 30% or more of the home value, we can expect a mortgage rate around 5-6%, and we would aim for 10 year loan.  We are looking to purchase a home for around that $140,00 ballpark.  In Moscow, there are options similar to a mortgage, but smaller timeframe and no interest. For instance 5 years. Not sure how that is even profitable, but it is an option (maybe that option is only direct with a seller in which case a jacked up price is what they are doing to make a 0 interest loan sensible...).

 

I just have no idea, should I use as much of my own cash as possible and minimize the loan amount, or given a certain loan rate and period, is there some benefit to taking out some loan of some percentage of the home value?

 

What would you do? Is there some mortgage interest rate under which it is advisable to take a loan and let one's money sit to continue earning?