What are the best suburbs for resale relatively close to Perth CBD and/or beach?

Since when did

1. Quinns-Rocks become close to the CBD
2. Quinns-Rocks become part of the metropolition area of Perth? It's like 50Km from the city!

It depends on your price-range. Most beach-side suburbs close to the Perth CBD (within 20-minutes drive) have a mean price above $1 million for a residential house.
In the northern suburbs, on value for money:
1. Sorrento - Mean $1.014m - 11 December 2011*
2. North Beach - Mean $1.07m - 11 August 2011*
3. Watermans Bay - Mean $1.23m - 11 July 2011*
*all statistics taken from www.realeastate.com.au
I haven't looked much into coastal properties south of the river - but be weary on the proportion of rental properties. You should receive solid ROI (return-on-investment) for North of the river/Western suburbs Perth beach-side residential properties valued under $1.5m. Conduct further independent research into into real estate values and price trends through reputable sources before purchasing.

I agree with Abby, Quinns Rocks is about 37 km from Perth city, about 30min down freeway and 12km from Joondalup based on google maps, in relation to resale find a better valued beach side suburb that would have the resale growth potential to this suburb.