In the past, conventional wisdom has always held that buying a two-year old, low-mileage, previously-owned vehicle represented the best value in a car purchase. Now, however, the auto industry -- especially as represented by the Detroit Big Three -- is feeling a world of hurt, hoping to sell 9 million units for the year when 15 million used to be a good number. What does this mean for the consumer?

• The return of zero percent financing.
• Sales and excise taxes on new vehicles bought in 2009 are tax deductible.
• Government backed warranties on GM and Chrysler vehicles.
• Retail prices slashed to their lowest level in years -- some as much as 30%.

By the end of 2009, prices are likely to stabilize, but right now, with dealerships going out of business and moving inventory key to automakers' long-term survival, deal-making is the word of the day.

Does this mean, then, that buying new cars is the best way to go? Yes and no. As always, there are multiple factors that go into any purchase:

• The buyer's individual financial picture.
• The ability to get needed financing.
• Vehicle form factor as weighed against needs.
• Fuel economy and long-term cost to maintain the vehicle purchased.

What the current situation does demand is better research and forethought from the prospective car buyer. All options should be considered, including used car purchases. Whereas two-year old previously-owned vehicles were once considered the sweet spot, cars that are only a few months old are finding their way back on to the market in both sales lots and via private transaction scenarios. If you are considering buying used, remember:

• If the car you are considering will be purchased through the previous owner, have the vehicle checked out by a mechanic of your choice.

• The best case scenario with any used car purchase is the presence of a complete and verifiable service record.

• Odometer fraud results in about $1 billion in consumer losses annually. The dash should be examined minutely for damage. Also look at the age of the title. A new title may have been obtained to hide mileage fraud.

• Whether working with a dealership or an individual, negotiate for a warranty of 60 to 90 days duration. Most issues will show up in that time, and you need recourse in the event of a problem.

• On fairly recent models, some amount of the original manufacturer's warranty may still apply. Be sure that warranty transfers with the sale.

• On all used car purchases, have the exact amount determined in writing before putting any money down. It is illegal for a used car salesman to increase the price of the vehicle at closing, but it does happen and many buyers don't realize the law is on their side.

• Before making any purchase, investigate and understand the "lemon laws" in your state. They may or may not apply to the purchase of a used car, but if they do, know what documentation you will need to seek a legal remedy.

Regardless of the route chosen -- used or new -- consumers are looking for the highest quality vehicle they can find at the best price point. In the presence of a good warranty, a used car can still offer as much value as a new purchase but tempting incentives are out there for the taking. Bottom line. Do your homework. Compare all aspects of total purchase price. And don't be afraid to negotiate.