In a perfect world scenario you would get a car 2-5 years old that has very little mileage. One of the long standing archaic rules of the car world is that age trumps mileage. This was a good rule when any idiot could roll back an odometer.
Chances are now that if you rolled your odometer back the car was serviced somewhere, had inspection or whatever and it is on a report. If seller was found to do this they could face jail time and obviously now their car is almost worthless.
Why do I mention this? Because you can take a look at 2011 cars. Those with 20K miles go for just a little more than those with 100K miles. As an owner you will start incurring heavy maintenance costs around 100K on most newer cars.
By buying cars with lower mileage, keeping them for a year or two, and reselling them before they get up in miles, you can stay in that magic area where you can drive a pretty good car for $200-300 a month. Note that this takes work on both the buying and selling side and you often need cash to get these cars (dealers are good about siphoning really good used cars to employees/friends).
This is a great strategy for keeping costs down and car value up but obviously a lot of people try to do this and it takes work and you have to be willing to settle sometimes on a car that is fine, but not exactly what you want.
As for leasing this really gets into three main components:
- price of car
- how long you want to keep it
- how good are you at buying/selling
If you are going to do EVERYTHING at a dealership and you want something new or newish you might as well lease. At least then you can shop around for apples to apples. The problem with buying a new/used car from the dealers in perpetuity isn't the buying process. It is the fact that they will screw you on the trade-in. A car that books for 20K may trade-in for 17K. Even if the dealer says they are giving you 20K, then they make you pay list price for the car.
I have many many times negotiated a price of a car and then wife brought in our car separately and I can count on ZERO fingers how many times that the dealership honored both sides of the negotiations. Not only did they not honor them but most refused to talk with us after they found out.
With a lease you don't have to worry about losing this money in the negotiations. You might pay a little extra (or not since you can shop around) but after the lease you wash your hands of the car.
The one caveat to this is the high-end market. When you are talking your Acura, Mercedes, Lexus... It is probably better to buy and trade in every couple years. You lose too much equity by leasing, where it won't cover the trade-in gap and cost of your money being elsewhere. I have a friend that does this and gets a slightly better car every 2-3 years with same monthly payment.
Another factor to consider is the price of a car. If your car will be worth over $15K at time of sale you are going to have a hard time selling it by owner. When amounts get this high people often need financing. Yes they can get personal financing but most people are too lazy to do this. So the number of used car buyers on let's say craigslist are way way fewer as you start getting over $10-12K and I have found $15K to be kind of that magic amount.
The pro-buy-used side is easy. Aim for those cars around $12-18K that are out there (and many still under warranty). These owners will have issues finding cash buyers. They will drop prices somewhere between book price and dealer trade-in. In lucky cases where they need cash maybe below dealer trade-in. And remember these sellers aren't dealing with 100s let alone 10 buyers. You drive the car for 3-4 years. Maybe it is $7-10K. But now you will get much much closer to book price because there will be far more buyers in this range.