Balance transfer advice

[crazy about cars]

A family friend has asked for some financial advise and I'm hoping for further input from PH.

He currently have 3 credit cards:

• Card 1 with main bank - 0 balance minimum credit limit.
• Card 2 - Active credit card. Currently have sizeable balance of around 5k
• Card 3 - Opened around 1.5 years ago to take advantage 0% balance transfer. Not much left and was told can afford to pay it off in 1 go

His plans are to:

• Close Card 1
• Transfer balance from Card 2 (and maybe Card 3) into a new 0% card and close down Card 3.

My concern is that his plans will somehow affect his credit history/profile. I believe he is also planning to apply for a mortgage in next 6 months or so.
Does having less credit card affect credit history? Should he just pay off Card 2 and not think about another balance transfer? He told me he could probably pay off Card 2 balance but would take sizeable chunk out of savings.