I am in a similar situation - I live in the inner city, with three trams at my front door, work in the CBD, so haven't owned a car in years. I rent cars 12-15 times a year, almost always on the weekend, and occasionally use share cars such as Flexi Car, Go Get and Green Car Share - not sure if car sharing is available in Perth. I find car sharing generally significantly more expensive than car rental, so only use it in an emergency.
I have joined all of the major 5 car rental companies - Hertz, Avis, Europcar, Thrifty and Budget. I joined them roughly in that order and I rent roughly in that order of preference, for both a cost and choice of car perspective (I'm 6'9", so prefer large cars, for both comfort and power). I also have access to corporate rates through Hertz and Avis through my employer. None have a cost to join. Given the number of times I rent, I can only obtain status with one company if I do most of my rentals with the same company. I just scraped in to Hertz 5 star last year, which doesn't really give me much that I wasn't already getting - often get upgrades anyway. It should be noted that only Hertz and Europcar have status, the others do not. I have found Avis to be pretty generous with upgrades. No upgrades with the others and often poor service. My worst experience has been with Europcar - overcharging and never credit points to Velocity, even when followed up. Really poor customer service. Hertz have had issues crediting points correctly, but have always fixed with only one contact through their website. Generally, I find being a member gives you better service than if you're not.
I never pay to reduce the excess - rely on two credit cards to cover the excess - Westpac Altitude Platinum, which covers up to $5,500 where I am the renter (enough to cover most situations) with a $250 excess and ANZ Car rental cover, which provides $2,400 cover with a $350 excess. ANZ also covers me where I am an additional driver but not the renter.
I Generally do not pay anymore than $50 a day for a Commodore SV6 or Falcon XR6 - often much less. Can often pay $30 a day.
Europcar will probably work best for you as their loyalty program has 20-30% discount depending on your level, and guaranteed upgrades.
I never spend more than $35/day (Hyundai i20) and have ended up with cars like Audi A4 and Subaru Forester.
If you can get to Virgin Gold, they'll give you complimentary Europcar Gold which will get you started.
Without Virgin Gold, Europcar Privilege will give you up to a 10% discount and no upgrade. If you obtain Virgin Gold, or rent more than 10 times a year, Europcar Privilege Executive gives up to a 20% discount and an upgrade. If you obtain Virgin Platinum or rent more than 25 times a year, Europcar Privilege Elite gives up to a 30% discount (up to 20% discount for domestic rentals), free additional driver and a few other benefits.
Can you please give some some details of $35/day rentals? How far in advance, where, etc. I can never get anywhere near that. Having said that, I never look at i20's as I have no intention of driving one! And I don't have status to obtain an upgrade.
I agree Europcar will be the best, should come to $20 a day for a four day or more rental if you collect Sun to Tue.
Can you please give some some details of $20/day rentals? How far in advance, where, etc.
Make a relationship with a local car rental office and they will look after you very nicely.
Good idea!