Thoughts on cash purchase?

[Jungae Park]

I prefer 20% down with 30 year mortgage 

Because it allows me to conserve my cash for future purchase (leverages) and gives me tax benefits since mortgage interest will be deductible. Also I get discounts if I can lock low interest rates against to inflation over 30 years. 

I'm complete newbie and considering to buy my very first rental unit. It's listed as cash only. 

My question is....

Would you go with full cash purchase?

If your answer is "depends on deals" then what is going to be your trigger in terms of ROI ?