recommended downpayment size

[Chi Wen]

I know there are different rules and personal preferences on this topic but I wanted to see what the general consensus was for my goals/objectives and the pros/cons of putting a small or large downpayment.

This would be my first house and, since I'm currently renting, it would be a place I would staying in. I'm hoping to get either a 2b/2b condo/townhouse because that's all I can afford and rent out one of the rooms.

Assuming I could afford the 20% down for a conventional mortgage, would it be smarter financially and investment-wise to try and put as less cash as possible and pay PMI or go the traditional route and pay 20% or more?

I've read a couple pro's to the 20% down is in case the market goes down and you want to sell - you're not going to be underwater. And of course your monthly payments are lower and no PMI. However the pro's of less cash down is your if the market turns sour you lose less while the bank bears most of the risk and it also frees you up with cash to potentially invest elsewhere.

But these are just from me reading and would like to hear the professional guru's opinions of which path would you take as a newbie in investing (or buying RE in general). 

thank you